T. Tsuchikawa, H. Kabeda, Shinki Oyabu, T. Kokusho, H. Kobayashi and Y. Toba : Spitzer/IRS Full Spectral Modeling to Characterize Mineralogical Properties of Silicate Dust in Heavily Obscured AGNs, The Astrophysical Journal, Vol.941, No.1, 50, 2022.
Satoshi Itoh, Daisuke Ishihara, Takehiko Wada, Takao Nakagawa, Shinki Oyabu, Hidehiro Kaneda and Yasuhiro Hirahara : Simulations of the spectral resolving power of a compact space-borne immersion-echelle spectrometer using mid-infrared wave tracing, Journal of Astronomical Telescopes, Instruments, and Systems, Vol.8, No.25004, 2022.
Shusuke Onishi, Takao Nakagawa, Shunsuke Baba, Kosei Matsumoto, Naoiki Isobe, Mai Shirahata, Hiroshi Terada, Tomonori Usuda and Shinki Oyabu : Study of the Inner Structure of the Molecular Torus in IRAS 08572+3915 NW with Velocity Decomposition of CO Rovibrational Absorption Lines, The Astrophysical Journal, Vol.921, No.141, 20pp, 2021.
L. Barchiesi, F. Pozzi, C. Vignali, J. F. Cerrera, F. Vita, F. Calura, L. BisiGello, G. Lanzuisi, C. Gruppioni, E Lusso, I. Delvecchio, M. Negrelo, A. Cooray, A. Feltre, A. J. Fernandez-Ontiveros, S. Gallerani, H. Kaneda, Shinki Oyabu, M. Pereira-Santaella, E. Piconcelli, C. Ricci, G. Rodighiero, L. Spinoglio and F. Tombesi : The role of SPICA-like missions and the Origins Space Telescope in the quest for heavily obscured AGN and synergies with Athena, Publications of the Astronomical Society of Australia, Vol.38, No.e033, 2021.
T. Tsuchikawa, H. Kaneda, Shinki Oyabu, T. Kokusho, H. Kobayashi, M. Yamagishi and Y. Toba : A systematic study of silicate absorption features in heavily obscured AGNs observed by Spitzer/IRS, Astronomy & Astrophysics, Vol.651, No.117, 21pp, 2021.
T. Suzuki, Shinki Oyabu, K. S. Ghosh, K. D. Ojha, H. Kaneda, H. Maeda, T. Nakagawa, P. J. Ninan, S. Vig, M. Hanaoka, F. Saito, S. Fujiwara and T. Kanayama : [CII] emission properties of the massive star-forming region RCW 36 in a filamentary molecular cloud, Astronomy & Astrophysics, Vol.651, A30-8pp, 2021.
(要約)
<BR /> Aims: We investigate the properties of [C II] 158 μm emission of RCW 36 in a dense filamentary cloud. <BR /> Methods: [C II] observations of RCW 36, covering an area of ~30' × 30', were carried out with a Fabry-Pérot spectrometer on board a 100-cm balloon-borne far-infrared (IR) telescope with an angular resolution of 90''. Using AKARI and Herschel images, we compared the spatial distribution of the [C II] intensity with the emission from the large grains and polycyclic aromatic hydrocarbon (PAH). <BR /> Results: The [C II] emission is in good spatial agreement with shell-like structures of a bipolar lobe observed in IR images, which extend along the direction perpendicular to the direction of cold dense filament. We found that the [C II]-160 μm relation for RCW 36 shows a higher brightness ratio of [C II]/160 μm than that for RCW 38, while the [C II]-9 μm relation for RCW 36 is in good agreement with that for RCW 38. <BR /> Conclusions: Via a spectral decomposition analysis on a pixel-by-pixel basis using IR images, the [C II] emission is spatially well correlated with PAH and cold dust emissions. This means that the observed [C II] emission predominantly comes from photo-dissociation regions. Moreover, the L<SUB>[C II]</SUB>/L<SUB>FIR</SUB> ratio shows large variation (10<SUP>-2</SUP>-10<SUP>-3</SUP>), as compared with the L<SUB>[C II]</SUB>/L<SUB>PAH</SUB> ratio. In view of the observed tight correlation between L<SUB>[C II]</SUB>/L<SUB>FIR</SUB> and the optical depth at λ = 160 μm, the large variation in L<SUB>[C II]</SUB>/L<SUB>FIR</SUB> can be simply explained by the geometrical effect, that is, L<SUB>FIR</SUB> has contributions from the entire dust-cloud column along the line of sight, while L<SUB>[C II]</SUB> has contributions from far-UV illuminated cloud surfaces. Based on the picture of the geometry effect, the enhanced brightness ratio of [C II]/160 μm is attributed to the difference in gas structures where massive stars are formed: filamentary (RCW 36) and clumpy (RCW 38) molecular clouds; thus suggesting that RCW 36 is dominated by far-UV illuminated cloud surfaces, as compared with RCW 38.
(キーワード)
dust / extinction / ISM: lines and bands / HII regions / ISM: individualobjects: RCW36 / Astrophysics - Astrophysics of Galaxies
Yoshiki Toba, Yoshihiro Ueda, Poshak Gandhi, Claudio Ricci, Denis Burgarella, Veronique Buat, Tohru Nagao, Shinki Oyabu, Hideo Matsuhara and Bau-Ching Hsieh : How Does the Polar Dust Affect the Correlation between Dust Covering Factor and Eddington Ratio in Type 1 Quasars Selected from the Sloan Digital Sky Survey Data Release 16?, The Astrophysical Journal, Vol.912, No.2, id91-15, 2021.
(要約)
We revisit the dependence of the covering factor (CF) of dust torus on physical properties of active galactic nuclei (AGNs) by taking into account an AGN polar dust emission. The CF is converted from a ratio of infrared (IR) luminosity contributed from AGN dust torus ( ${L}_{athrm{IR}}^{athrm{torus}}$ ) and AGN bolometric luminosity (L<SUB>bol</SUB>), by assuming a nonlinear relation between luminosity ratio and intrinsic CF. We select 37,181 type 1 quasars at z < 0.7 from the Sloan Digital Sky Survey Data Release 16 quasar catalog. Their L<SUB>bol</SUB>, black hole mass (M<SUB>BH</SUB>), and Eddington ratio (λ<SUB>Edd</SUB>) are derived by spectral fitting with QSFit. We conduct spectral energy distribution decomposition by using X-CIGALE with a clumpy torus and polar dust model to estimate ${L}_{athrm{IR}}^{athrm{torus}}$ without being affected by the contribution of stellar and AGN polar dust to IR emission. For 5752 quasars whose physical quantities are securely determined, we perform a correlation analysis on CF and (i) L<SUB>bol</SUB>, (ii) M<SUB>BH</SUB>, and (iii) λ<SUB>Edd</SUB>. As a result, anticorrelations for CF-L<SUB>bol</SUB>, CF-M<SUB>BH</SUB>, and CF-λ<SUB>Edd</SUB> are confirmed. We find that incorporating the AGN polar dust emission makes those anticorrelations stronger compared to those without considering it. This indicates that polar dust wind probably driven by AGN radiative pressure is one of the key components to regulate obscuring material of AGNs.
(キーワード)
Quasars / Supermassive black holes / Catalogs / 1319 / 1663 / 205 / Astrophysics - Astrophysics of Galaxies / Astrophysics - High EnergyAstrophysical Phenomena
Risako Katayama, Hidehiro Kaneda, Takuma Kokusho, Kumiko Morihana, Toyoaki Suzuki, Shinki Oyabu, Mitsuyoshi Yamagishi and Takuro Tsuchikawa : Hydrogen recombination near-infrared line mapping of Centaurus A with IRSF/SIRIUS, Publications of the Astronomical Society of Japan, Vol.72, No.5, id.88-8pp, 2020.
(要約)
Centaurus A (Cen A) is one of the most famous galaxies hosting an active galactic nucleus (AGN), where the interaction between AGN activities and surrounding interstellar and intergalactic media has been investigated. Recent studies reported detections of Hα emission from clouds in the galactic halo toward the northeast and southwest of the nucleus of Cen A, suggesting that AGN jets may have triggered star formation there. We performed near-infrared line mapping of Cen A with the IRSF 1.4 m telescope, using the narrow-band filter tuned for Paβ, from which we find that Paβ emission is not detected significantly from either of the northeast or southwest regions. The upper limit of the Paβ/Hα ratio in the northeast region is compatible with that expected for a typical H II region, in line with the scenario that AGNs have triggered star formation there. On the other hand, the upper limit of Paβ/Hα in the southwest region is significantly lower than that expected for a typical H II region. A possible explanation of the low Paβ/Hα ratio in the southwest region is the scattering of Hα and Paβ photons from the center of Cen A by dust grains in the halo clouds. From the upper limit of Paβ/Hα in the southwest region, we obtain constraints on the dust size distribution, which is found to be compatible with those seen in the interstellar medium of our Galaxy.
(キーワード)
galaxies: halos / galaxies: individual (Centaurus A) / infrared:galaxies / scattering / Astrophysics - Astrophysics of Galaxies
Yoshiki Toba, Tomotsugu Goto, Nagisa Oi, Ting-Wen Wang, Jin Seong Kim, -C. Simon C. Ho, Denis Burgarella, Tetsuya Hashimoto, Bau-Ching Hsieh, Ting-Chi Huang, Seong Ho Hwang, Hiroyuki Ikeda, K. Helen Kim, Seongjae Kim, Dongseob Lee, A. Matthew Malkan, Hideo Matsuhara, Takamitsu Miyaji, Rieko Momose, Youichi Ohyama, Shinki Oyabu, Chris Pearson, D. Daryl Joe Santos, Hyunjin Shim, Toshinobu Takagi, Yoshihiro Ueda, Yousuke Utsumi and Takehiko Wada : Search for Optically Dark Infrared Galaxies without Counterparts of Subaru Hyper Suprime-Cam in the AKARI North Ecliptic Pole Wide Survey Field, The Astrophysical Journal, Vol.899, No.1, id.35-17pp, 2020.
(要約)
We present the physical properties of AKARI sources without optical counterparts in optical images from the Hyper Suprime-Cam (HSC) on the Subaru telescope. Using the AKARI infrared (IR) source catalog and HSC optical catalog, we select 583 objects that do not have HSC counterparts in the AKARI North Ecliptic Pole wide survey field (∼5 deg<SUP>2</SUP>). Because the HSC limiting magnitude is deep (g<SUB>AB</SUB> ∼ 28.6), these are good candidates for extremely red star-forming galaxies (SFGs) and/or active galactic nuclei (AGNs), possibly at high redshifts. We compile multiwavelength data out to 500 μm and use them for fitting the spectral energy distribution with CIGALE to investigate the physical properties of AKARI galaxies without optical counterparts. We also compare their physical quantities with AKARI mid-IR selected galaxies with HSC counterparts. The estimated redshifts of AKARI objects without HSC counterparts range up to z ∼ 4, significantly higher than for AKARI objects with HSC counterparts. We find that (i) 3.6 - 4.5 μm color, (ii) AGN luminosity, (iii) stellar mass, (iv) star formation rate, and (v) V-band dust attenuation in the interstellar medium of AKARI objects without HSC counterparts are systematically larger than those of AKARI objects with counterparts. These results suggest that our sample includes luminous, heavily dust-obscured SFGs/AGNs at z ∼ 1-4 that are missed by previous optical surveys, providing very interesting targets for the coming era of the James Webb Space Telescope.
Misaki Hanaoka, Hidehiro Kaneda, Toyoaki Suzuki, Takuma Kokusho, Shinki Oyabu, Daisuke Ishihara, Mikito Kohno, Takuya Furuta, Takuro Tsuchikawa and Futoshi Saito : A systematic study of Galactic infrared bubbles along the Galactic plane with AKARI and Herschel. II. Spatial distributions of dust components around the bubbles, Publications of the Astronomical Society of Japan, Vol.72, No.1, 5, 2020.
(要約)
Galactic infrared (IR) bubbles, which can be seen as shell-like structures at mid-IR wavelengths, are known to possess massive stars within their shell boundaries. In our previous study (Hanaoka, 2019, PASJ, 71, 6), we expanded the research area to the whole Galactic plane (0° ? l ? 360°, |b| ? 5°) and studied systematic differences in the shell morphology and the IR luminosity of the IR bubbles between inner and outer Galactic regions. In this study, utilizing high spatial- resolution data of AKARI and WISE in the mid-IR and Herschel in the far- IR, we investigate the spatial distributions of dust components around each IR bubble to discuss the relation between the star-formation activity and the dust properties of the IR bubbles. For the 247 IR bubbles studied in Hanaoka (2019, PASJ, 71, 6), 165 IR bubbles are investigated in this study, which have the Herschel data (|b|? 1°) and known distances. We created their spectral energy distributions on a pixel-by-pixel basis around each IR bubble, and decomposed them with a dust model consisting of polycyclic aromatic hydrocarbons (PAHs), hot dust, warm dust and cold dust. As a result, we find that the offsets of dust heating sources from the shell centers in inner Galactic regions are systematically larger than those in outer Galactic regions. Many of the broken bubbles in inner Galactic regions show large angles between the offset and the direction of the broken shell from the center. Moreover, the spatial variations of the PAH intensity and cold dust emissivity around the IR bubbles in inner Galactic regions are larger than those in outer Galactic regions. We discuss these results in light of the interstellar environments and the formation mechanism of the massive stars associated with the IR bubbles.
(キーワード)
infrared: ISM / ISM: bubbles / stars: formation / stars: massive / Astrophysics - Astrophysics of Galaxies
T. Tsuchikawa, H. Kaneda, Shinki Oyabu, T. Kokusho, K. Morihana, H. Kobayashi, M. Yamagishi and Y. Toba : Near- to mid-infrared spectroscopy of the heavily obscured AGN LEDA 1712304 with AKARI/IRC, Astronomy & Astrophysics, Vol.626, A130, 2019.
(要約)
Context. Although heavily obscured active galactic nuclei (AGNs) have been found by many observational studies, the properties of the surrounding dust are poorly understood. Using AKARI/IRC spectroscopy, we discovered a new heavily obscured AGN in LEDA 1712304 which shows a deep spectral absorption feature due to silicate dust. Aims: We study the infrared (IR) spectral properties of circumnuclear silicate dust in LEDA 1712304. Methods: We performed IR spectral fitting, considering silicate dust properties such as composition, porosity, size, and crystallinity. Spectral energy distribution fitting was also performed on the flux densities in the UV to submillimeter range to investigate the global spectral properties. Results: The best-fit model indicates 0.1 μm-sized porous amorphous olivine (Mg2xFe2-2xSiO4; x = 0.4) with 4% crystalline pyroxene. The optical depth is τsil ? 2.3, while the total IR luminosity and stellar mass are estimated to be LIR = (5 ± 1)×1010 L? and Mstar = (2.7 ± 0.8)×109 M?, respectively. In such low LIR and Mstar ranges, there are few galaxies that show such a large τsil. Conclusion. The silicate dust in the AGN torus of LEDA 1712304 has properties that are notably similar to those in other AGNs overall, but slightly different in the wing shape of the absorption profile. The porosity of the silicate dust suggests dust coagulation or processing in the circumnuclear environments, while the crystallinity suggests that the silicate dust is relatively fresh.
Hoon Ji Kim, Myungshin Im, Dohyeong Kim, Jong-Hak Woo, Marios Karouzos, Mok Hyung Lee, Gyoon Myung Lee, D. Hyunsung Jun, Takao Nakagawa, Hideo Matsuhara, Takehiko Wada, Shinki Oyabu, Toshinobu Takagi and Youichi Ohyama : The interplay between active galactic nuclei and star formation activities of type 1 active galactic nuclei probed by polycyclic aromatic hydrocarbon 3.3 μm emission feature with AKARI, Publications of the Astronomical Society of Japan, Vol.71, No.2, 25, 2019.
(要約)
We investigate the connection between active galactic nucleus (AGN) and star formation activities of AGN host galaxies by studying the 3.3 μm polycyclic aromatic hydrocarbon (PAH) emission feature of 79 type 1 AGNs using the AKARI space telescope. Utilizing the slitless spectroscopic capability of the AKARI Infrared Camera, we obtained the spectra in the wavelength range of 2-5 μm from extended regions of the sample galaxies in order to measure star formation activity from the entire host galaxies. We detected the 3.3 μm PAH emission feature from 18 sample galaxies and measured the luminosities of the feature (LPAH3.3). We found that LPAH3.3 is significantly correlated with AGN luminosities (LAGN), such as 5100 ? monochromatic luminosity, and X-ray luminosity regardless of host galaxy morphology and radio-loudness. The correlation between LPAH3.3 and LAGN follows LPAH3.3 ∝ LAGN^{0.9}. Therefore we suggest that host galaxies with stronger AGN activities have stronger star formation activities. We also found that the ratios between LPAH3.3 and the bolometric infrared luminosity (LIR) of our sample galaxies are lower than for non-AGN galaxies due to increased LIR. We suggest that this can be attributed to the contribution of AGN to LIR.
(キーワード)
black hole physics / galaxies: active / galaxies: Seyfert / galaxies: star formation / quasars: general
Tímea O Kovács, Denis Burgarella, Hidehiro Kaneda, Dániel Cs Molnár, Shinki Oyabu, Sandor Pinter and Viktor L. Toth : Star formation and polycyclic aromatic hydrocarbons in ELAIS N1 galaxies as seen by AKARI, Publications of the Astronomical Society of Japan, Vol.71, No.2, 27, 2019.
(要約)
We have examined the relationship between star formation and polycyclic aromatic hydrocarbons (PAHs) in a variety of galaxies. PAHs are excited by the ultraviolet photons of young stars, but they are disassociated by strong UV radiation in starbursts. Therefore their emission (which is in the wavelength range covered by AKARI) can be used as a star formation tracer in main sequence galaxies. We selected our targets in the ELAIS N1 field with AKARI detections, matched them with the Herschel Point Source Catalog, and collected other publicly available photometric data. Their spectral energy distributions (SEDs) were fitted, and several parameters of the galaxies were estimated, e.g., star formation rate (SFR), stellar mass, and the fraction of PAHs compared to dust mass (qPAH), and we examined the relationships between these parameters. The final sample consisted of 48 galaxies, with redshifts from 0.04 to 2.36. The estimated qPAH values were lower on average than typical values in the literature. This could be due to various reasons, such as low metallicity, or ongoing active galactic nucleus or starburst activity. Of our sample, 83% of the objects fell in the star-forming main sequence of galaxies, while only 8% could be considered as starbursts. We found a decreasing qPAH trend with increasing AV and consequently LIR, suggesting the possible presence of compact star-forming regions. We compared the qPAH values with the known relations of the PAH luminosities, but they did not always follow the same trends (SFR, LIR), and showed only slight correlation with the PAH luminosities.
(キーワード)
galaxies: ISM / galaxies: star formation / infrared: galaxies
Misaki Hanaoka, Hidehiro Kaneda, Toyoaki Suzuki, Takuma Kokusho, Shinki Oyabu, Daisuke Ishihara, Mikito Kohno, Takuya Furuta, Takuro Tsuchikawa and Futoshi Saito : A systematic study of Galactic infrared bubbles along the Galactic plane with AKARI and Herschel, Publications of the Astronomical Society of Japan, Vol.71, No.1, 6, 2019.
(要約)
Galactic infrared (IR) bubbles, which have shell-like structures in the mid-IR wavelengths, are known to contain massive stars near their centers. Infrared bubbles in inner Galactic regions (|l| ? 65°, |b| ? 1°) have so far been studied well to understand the massive star formation mechanisms. In this study, we expand the research area to the whole Galactic plane (0° ? l < 360°, |b| ? 5°), using the AKARI all- sky survey data. We limit our study to large bubbles with angular radii of >1' to reliably identify and characterize them. For the 247 IR bubbles in total, we derived the radii and the covering fractions of the shells, based on the method developed by Y. Hattori et al. (2016, PASJ, 68, 37). We also created their spectral energy distributions, using the AKARI and Herschel photometric data, and decomposed them with a dust model to obtain the total IR luminosity and the luminosity of each dust component, i.e., polycyclic aromatic hydrocarbons (PAHs), warm dust, and cold dust. As a result, we find that there are systematic differences in the IR properties of the bubbles between the inner and outer Galactic regions. The total IR luminosities are lower in outer Galactic regions, while there is no systematic difference in the range of the shell radii between inner and outer Galactic regions. More IR bubbles tend to be observed as broken bubbles rather than closed ones and the fractional luminosities of the PAH emission are significantly higher in outer Galactic regions. We discuss the implications of these results for the massive stars and the interstellar environments associated with the Galactic IR bubbles.
(キーワード)
infrared: ISM / ISM: bubbles / star: formation / star: massive / Astrophysics - Astrophysics of Galaxies
Toyoaki Suzuki, Hidehiro Kaneda, Takehiko Wada, Souta Ukai, Misaki Hanaoka, Kazuyuki Shichi, Hiroki Maeda, Shinki Oyabu and Kentaroh Watanabe : Evaluation of the compensation ratio of heavily-Ga doped Ge for far-infrared detectors in astronomy, Japanese Journal of Applied Physics, Vol.57, No.11, 116701, 2018.
(要約)
Ge-based blocked impurity band detectors fabricated with the surface- activated wafer bonding (SAB) method are expected to realize larger format arrays for far-infrared astronomical observations. To make sensitive p-type Ge detectors, the minor impurity (N D) concentration of a heavily-impurity doped Ge wafers is required to be <1014 cm-3 in addition to the major impurity (N A) concentration of ?1016 cm-3. Thus, a compensation ratio K (= N D/N A) below 10-2 should be achieved in advance to SAB. We measured the resistivity and carrier density of heavily-Ga doped Ge wafers at temperatures of 3-300 K. However, N D and N A of the wafers cannot be obtained from the conventional model for p-type semiconductors due to the significant contribution of the impurity band conduction (IBC). Then, an extended model including the IBC process was constructed, which was found to well reproduce the measured data over the whole temperature range. From the values obtained from the model fitting, it is revealed that our heavily-Ga doped Ge wafers show N A ? 1016 cm-3 with ultra-low K below 10-3.
Y. Ohyama, T. Wada, H. Matsuhara, T. Takagi, M. Malkan, T. Goto, E. Egami, -M. H. Lee, M. Im, H. J. Kim, C. Pearson, H. Inami, Shinki Oyabu, F. Usui, D. Burgarella, F. Mazyed, M. Imanishi, -S. W. Jeong, T. Miyaji, J. Díaz Tello, T. Nakagawa, S. Serjeant, T. T. Takeuchi, Y. Toba, J. G. White, H. Hanami and T. Ishigaki : AKARI mid-infrared slitless spectroscopic survey of star-forming galaxies at z ≲ 0.5, Astronomy & Astrophysics, Vol.618, A101, 2018.
(要約)
Context. Deep mid-infrared (MIR) surveys have revealed numerous strongly star-forming galaxies at redshift z ? 2. Their MIR fluxes are produced by a combination of continuum and polycyclic aromatic hydrocarbon (PAH) emission features. The PAH features can dominate the total MIR flux, but are difficult to measure without spectroscopy. Aims: We aim to study star-forming galaxies by using a blind spectroscopic survey at MIR wavelengths to understand evolution of their star formation rate (SFR) and specific SFR (SFR per stellar mass) up to z ? 0.5, by paying particular attention to their PAH properties. Methods: We conducted a low-resolution (R ? 50) slitless spectroscopic survey at 5-13 μm of 9 μm flux-selected sources (>0.3 mJy) around the north ecliptic pole with the infrared camera (IRC) onboard AKARI. After removing 11 AGN candidates by using the IRC photometry, we identify 48 PAH galaxies with PAH 6.2, 7.7, and 8.6 μm features at z < 0.5. The rest-frame optical-MIR spectral energy distributions (SEDs) based on CFHT and IRC imaging covering 0.37-18 μm were produced, and analysed in conjunction with the PAH spectroscopy. We defined the PAH enhancement by using the luminosity ratio of the 7.7 μm PAH feature over the 3.5 μm stellar component of the SEDs. Results: The rest-frame SEDs of all PAH galaxies have a universal shape with stellar and 7.7 μm bumps, except that the PAH enhancement significantly varies as a function of the PAH luminosities. We identify a PAH-enhanced population at z ? 0.35, whose SEDs and luminosities are typical of luminous infrared galaxies. They show particularly larger PAH enhancement at high luminosity, implying that they are vigorous star-forming galaxies with elevated specific SFR. Our composite starburst model that combines a very young and optically very thick starburst with a very old population can successfully reproduce most of their SED characteristics, although we cannot confirm this optically think component from our spectral analysis.
(キーワード)
galaxies: starburst / infrared: galaxies / galaxies: active / galaxies: evolution / Astrophysics - Astrophysics of Galaxies
R. P. Roelfsema, H. Shibai, L. Armus, D. Arrazola, M. Audard, D. M. Audley, M. C. Bradford, I. Charles, P. Dieleman, Y. Doi, L. Duband, M. Eggens, J. Evers, I. Funaki, R. J. Gao, M. Giard, A. Giorgio di, M. Fern?ndez L. Gonz?lez, M. Griffin, P. F. Helmich, R. Hijmering, R. Huisman, D. Ishihara, N. Isobe, B. Jackson, H. Jacobs, W. Jellema, I. Kamp, H. Kaneda, M. Kawada, F. Kemper, F. Kerschbaum, P. Khosropanah, K. Kohno, P. P. Kooijman, O. Krause, J. der Kuur van, J. Kwon, M. W. Laauwen, G. Lange de, B. Larsson, D. Loon van, C. S. Madden, H. Matsuhara, F. Najarro, T. Nakagawa, D. Naylor, H. Ogawa, T. Onaka, Shinki Oyabu, A. Poglitsch, V. Reveret, L. Rodriguez, L. Spinoglio, I. Sakon, Y. Sato, K. Shinozaki, R. Shipman, H. Sugita, T. Suzuki, S. der Tak F. F. van, J. Redondo Torres, T. Wada, Y. S. Wang, K. C. Wafelbakker, H. Weers van, S. Withington, B. Vandenbussche, T. Yamada and I. Yamamura : SPICA-A Large Cryogenic Infrared Space Telescope: Unveiling the Obscured Universe, Publications of the Astronomical Society of Australia, Vol.35, e030, 2018.
(要約)
Measurements in the infrared wavelength domain allow direct assessment of the physical state and energy balance of cool matter in space, enabling the detailed study of the processes that govern the formation and evolution of stars and planetary systems in galaxies over cosmic time. Previous infrared missions revealed a great deal about the obscured Universe, but were hampered by limited sensitivity.
(キーワード)
infrared: galaxies / infrared: general / infrared: planetary systems / instrumentation: photometers / instrumentation: spectrographs / space vehicles: instruments / Astrophysics - Instrumentation and Methods for Astrophysics
Misaki Hanaoka, Hidehiro Kaneda, Toyoaki Suzuki, Takuma Kokusho, Shinki Oyabu and Daisuke Ishihara : A systematic study of Galactic infrared bubbles along the whole Galactic plane with the AKARI all-sky surveys, The Cosmic Wheel and the Legacy of the AKARI Archive: From Galaxies and Stars to Planets and Life, 317, 2018.
(要約)
Galactic infrared (IR) bubbles are known to contain massive stars near their centers, and crucial to study massive star formation mechanisms. In our previous study (Hattori et al. 2016), IR bubbles located in inner Galactic regions (absolute value of l less than or equal to 65 deg, absolute value of b less than or equal to 1 deg) are classified into broken and closed bubbles, depending on their morphologies, to find that the broken bubbles are indicative of cloud-cloud collision. We expand the previous study to the whole Galactic plane using the AKARI all-sky survey data. We limit our study on large (R greater than 1') bubbles to reliably identify and classify them even in outer Galactic regions and relatively high-latitude regions where neither Spitzer nor Herschel data are available. As a result, we newly discover about 100 Galactic IR bubbles in outer Galactic regions (absolute value of l greater than 65 deg, absolute value of b less than or equal to 5 deg). We find that a significantly higher fraction of bubbles are classified into broken ones in outer Galactic regions than in inner Galactic regions. Following the same procedure as in Hattori et al. (2016), we also examine the properties of the bubbles, decomposing their spectral energy distributions consisting of AKARI and Herschel photometric data with a dust model. In the paper, we show the result of our comparative study on the properties of the Galactic IR bubbles between the inner and outer Galactic regions, and discuss the cause of their systematic difference.
(キーワード)
Bubbles / Milky Way / Massive star formation / ISM / Dust extinction
L. Katsuhiro Murata, Rika Yamada, Shinki Oyabu, Hidehiro Kaneda, Daisuke Ishihara, Mitsuyoshi Yamagishi, Takuma Kokusho and T. Tsutomu Takeuchi : A relationship of polycyclic aromatic hydrocarbon features with galaxy merger in star-forming galaxies at z < 0.2, Monthly Notices of the Royal Astronomical Society, Vol.472, No.1, 39, 2017.
(要約)
Using the AKARI, Wide-field Infrared Survey Explorer (WISE), Infrared Astronomical Satellite (IRAS), Sloan Digital Sky Survey (SDSS) and Hubble Space Telescope (HST) data, we investigated the relation of polycyclic aromatic hydrocarbon (PAH) mass (MPAH), very small grain mass (MVSG), big grain mass (MBG) and stellar mass (Mstar) with galaxy merger for 55 star-forming galaxies at redshift z < 0.2. Using the SDSS image at z < 0.1 and the HST image at z > 0.1, we divided the galaxies into merger galaxies and non-merger galaxies with the morphological parameter asymmetry A, and quantified merging stages of galaxies based on the morphological indicators, the second-order momentum of the brightest 20 per cent region M20 and the Gini coefficient. We find that MPAH/MBG of merger galaxies tend to be lower than that of non-merger galaxies and there are no systematic differences of MVSG/MBG and MBG/Mstar between merger galaxies and non-merger galaxies. We find that galaxies with very low MPAH/MBG seem to be merger galaxies at late stages. These results suggest that PAHs are partly destroyed at late stages of merging processes. Furthermore, we investigated MPAH/MBG variations in radiation field intensity strength G0 and the emission line ratio of [O I] λ 6300/Hα that is a shock tracer for merger galaxies and find that MPAH/MBG decreases with increasing both G0 and [O I]/Hα. PAH destruction is likely to be caused by two processes: strong radiation fields and large-scale shocks during merging processes of galaxies.
J. A. Fernández-Ontiveros, L. Armus, M. Baes, J. Bernard-Salas, D. A. Bolatto, J. Braine, L. Ciesla, I. Looze De, E. Egami, J. Fischer, M. Giard, E. Gonz?lez-Alfonso, L. G. Granato, C. Gruppioni, M. Imanishi, D. Ishihara, H. Kaneda, S. Madden, M. Malkan, H. Matsuhara, M. Matsuura, T. Nagao, F. Najarro, T. Nakagawa, T. Onaka, Shinki Oyabu, M. Pereira-Santaella, I. Fournon P?rez, P. Roelfsema, P. Santini, L. Silva, T. J. -D. Smith, L. Spinoglio, F. der Tak van, T. Wada and R. Wu : SPICA and the Chemical Evolution of Galaxies: The Rise of Metals and Dust, Publications of the Astronomical Society of Australia, Vol.34, e053, 2017.
(要約)
The physical processes driving the chemical evolution of galaxies in the last 11Gyr cannot be understood without directly probing the dust- obscured phase of star-forming galaxies and active galactic nuclei. This phase, hidden to optical tracers, represents the bulk of the star formation and black hole accretion activity in galaxies at 1 < z < 3. Spectroscopic observations with a cryogenic infrared observatory like SPICA, will be sensitive enough to peer through the dust-obscured regions of galaxies and access the rest-frame mid- to far-infrared range in galaxies at high-z. This wavelength range contains a unique suite of spectral lines and dust features that serve as proxies for the abundances of heavy elements and the dust composition, providing tracers with a feeble response to both extinction and temperature. In this work, we investigate how SPICA observations could be exploited to understand key aspects in the chemical evolution of galaxies: the assembly of nearby galaxies based on the spatial distribution of heavy element abundances, the global content of metals in galaxies reaching the knee of the luminosity function up to z 3, and the dust composition of galaxies at high-z. Possible synergies with facilities available in the late 2020s are also discussed.
L. Spinoglio, A. Alonso-Herrero, L. Armus, M. Baes, J. Bernard-Salas, S. Bianchi, M. Bocchio, A. Bolatto, C. Bradford, J. Braine, J. F. Carrera, L. Ciesla, L. D. Clements, H. Dannerbauer, Y. Doi, A. Efstathiou, E. Egami, J. A. Fernández-Ontiveros, A. Ferrara, J. Fischer, A. Franceschini, S. Gallerani, M. Giard, E. Gonz?lez-Alfonso, C. Gruppioni, P. Guillard, E. Hatziminaoglou, M. Imanishi, D. Ishihara, N. Isobe, H. Kaneda, M. Kawada, K. Kohno, J. Kwon, S. Madden, A. M. Malkan, S. Marassi, H. Matsuhara, M. Matsuura, G. Miniutti, K. Nagamine, T. Nagao, F. Najarro, T. Nakagawa, T. Onaka, Shinki Oyabu, A. Pallottini, L. Piro, F. Pozzi, G. Rodighiero, P. Roelfsema, I. Sakon, P. Santini, D. Schaerer, R. Schneider, D. Scott, S. Serjeant, H. Shibai, T. J. -D. Smith, E. Sobacchi, E. Sturm, T. Suzuki, L. Vallini, F. der Tak van, C. Vignali, T. Yamada, T. Wada and L. Wang : Galaxy Evolution Studies with the SPace IR Telescope for Cosmology and Astrophysics (SPICA): The Power of IR Spectroscopy, Publications of the Astronomical Society of Australia, Vol.34, e057, 2017.
(要約)
IR spectroscopy in the range 12-230 μm with the SPace IR telescope for Cosmology and Astrophysics (SPICA) will reveal the physical processes governing the formation and evolution of galaxies and black holes through cosmic time, bridging the gap between the James Webb Space Telescope and the upcoming Extremely Large Telescopes at shorter wavelengths and the Atacama Large Millimeter Array at longer wavelengths. The SPICA, with its 2.5-m telescope actively cooled to below 8 K, will obtain the first spectroscopic determination, in the mid-IR rest-frame, of both the star-formation rate and black hole accretion rate histories of galaxies, reaching lookback times of 12 Gyr, for large statistically significant samples. Densities, temperatures, radiation fields, and gas-phase metallicities will be measured in dust- obscured galaxies and active galactic nuclei, sampling a large range in mass and luminosity, from faint local dwarf galaxies to luminous quasars in the distant Universe. Active galactic nuclei and starburst feedback and feeding mechanisms in distant galaxies will be uncovered through detailed measurements of molecular and atomic line profiles. The SPICA's large-area deep spectrophotometric surveys will provide mid-IR spectra and continuum fluxes for unbiased samples of tens of thousands of galaxies, out to redshifts of z 6.
H. Kaneda, D. Ishihara, Shinki Oyabu, M. Yamagishi, T. Wada, L. Armus, M. Baes, V. Charmandaris, B. Czerny, A. Efstathiou, A. J. Fern?ndez-Ontiveros, A. Ferrara, E. Gonz?lez-Alfonso, M. Griffin, C. Gruppioni, E. Hatziminaoglou, M. Imanishi, K. Kohno, J. Kwon, T. Nakagawa, T. Onaka, F. Pozzi, D. Scott, T. J. -D. Smith, L. Spinoglio, T. Suzuki, F. der Tak van, M. Vaccari, C. Vignali and L. Wang : Unbiased Large Spectroscopic Surveys of Galaxies Selected by SPICA Using Dust Bands, Publications of the Astronomical Society of Australia, Vol.34, e059, 2017.
(要約)
The mid-infrared range contains many spectral features associated with large molecules and dust grains such as polycyclic aromatic hydrocarbons and silicates. These are usually very strong compared to fine-structure gas lines, and thus valuable in studying the spectral properties of faint distant galaxies. In this paper, we evaluate the capability of low-resolution mid-infrared spectroscopic surveys of galaxies that could be performed by SPICA. The surveys are designed to address the question how star formation and black hole accretion activities evolved over cosmic time through spectral diagnostics of the physical conditions of the interstellar/circumnuclear media in galaxies. On the basis of results obtained with Herschel far-infrared photometric surveys of distant galaxies and Spitzer and AKARI near- to mid-infrared spectroscopic observations of nearby galaxies, we estimate the numbers of the galaxies at redshift z > 0.5, which are expected to be detected in the polycyclic aromatic hydrocarbon features or dust continuum by a wide (10 deg2) or deep (1 deg2) blind survey, both for a given observation time of 600 h. As by-products of the wide blind survey, we also expect to detect debris disks, through the mid-infrared excess above the photospheric emission of nearby main- sequence stars, and we estimate their number. We demonstrate that the SPICA mid-infrared surveys will efficiently provide us with unprecedentedly large spectral samples, which can be studied further in the far-infrared with SPICA.
(キーワード)
galaxies: active / galaxies: evolution / galaxies: star formation / infrared: galaxies / infrared: ISM / methods: observational / Astrophysics - Astrophysics of Galaxies
Kimiaki Kawara, Yoshiki Matsuoka, Kei Sano, D. Timothy Brandt, Hiroaki Sameshima, Kohji Tsumura, Shinki Oyabu and Nobuyuki Ienaka : Ultraviolet to optical diffuse sky emission as seen by the Hubble Space Telescope Faint Object Spectrograph, Publications of the Astronomical Society of Japan, Vol.69, No.2, 31, 2017.
(要約)
We present an analysis of the blank-sky spectra observed with the Faint Object Spectrograph on board the Hubble Space Telescope. We study the diffuse sky emission from ultraviolet to optical wavelengths, which is composed of zodiacal light (ZL), diffuse Galactic light (DGL), and residual emission. The observations were performed towards 54 fields distributed widely over the sky, with spectral coverage from 0.2 to 0.7 μm. In order to avoid contaminating light from earthshine, we use the data collected only in orbital nighttime. The observed intensity is decomposed into the ZL, DGL, and residual emission, in eight photometric bands spanning our spectral coverage. We found that the derived ZL reflectance spectrum is flat in the optical, which indicates major contribution of C-type asteroids to the interplanetary dust (IPD). In addition, the ZL reflectance spectrum has an absorption feature at ?0.3 μm. The shape of the DGL spectrum is consistent with those found in earlier measurements and model predictions. While the residual emission contains a contribution from the extragalactic background light, we found that the spectral shape of the residual looks similar to the ZL spectrum. Moreover, its optical intensity is much higher than that measured from beyond the IPD cloud by Pioneer 10/11, and also than that of the integrated galaxy light. These findings may indicate the presence of an isotropic ZL component, which is missed in the conventional ZL models.
Hidetoshi Sano, Tomoya Amatsutsu, Toru Kondo, Keichiro Nakamichi, Mitsuyoshi Yamagishi, Daisuke Ishihara, Shinki Oyabu, Hidehiro Kaneda, Kengo Tachihara and Yasuo Fukui : A Quality Check of the Akari Mid-Infrared All-Sky Diffuse Map Toward the Massive Star-Forming Regions NGC 6334 and NGC 6357, Publications of The Korean Astronomical Society, Vol.32, No.1, 21-23, 2017.
(要約)
We present a comparative study of CO and polycyclic aromatic hydrocarbon (PAH) emission toward a region including the massive star-forming regions of NGC 6334 and NGC 6357. We use the NANTEN12CO($J$ = 1-- 0) data and the $AKARI$ 9 $u$m All-Sky diffuse map in order to evaluate the calibration accuracy of the $AKARI$ data. We confirm that the overall CO distribution shows a good spatial correspondence with the PAH emission, and their intensities exhibit a good power-law correlation with a spatial resolution down to 4$'$ over the region of 10circimes10circ. We also reveal poorer correlation for small scale structures between the two quantities toward NGC 6357, due to strong UV radiation from local sources. Larger scatter in the correlation toward NGC 6357 indicates higher ionization degree and/or PAH excitation than that of NGC 6334.
Tomoya Amatsutsu, Daisuke Ishihara, Toru Kondo, Hidehiro Kaneda, Shinki Oyabu, Mitsuyoshi Yamagishi, Keichiro Nakamichi, Hidetoshi Sano and Takashi Onaka : The Current Status of the Akari Mid-Infrared All-Sky Diffuse Maps, Publications of The Korean Astronomical Society, Vol.32, No.1, 25-27, 2017.
Mitsuyoshi Yamagishi, Hidehiro Kaneda, Shinki Oyabu, Daisuke Ishihara, Takashi Onaka, Takashi Shimonishi and Toyoaki Suzuki : Study of CO2/H2O Ice Abundance Ratios in Nearby Galaxies with the Akari Near-Infrared Spectroscopy, Publications of The Korean Astronomical Society, Vol.32, 141, 2017.
Takuma Kokusho, Hidehiro Kaneda, Toru Kondo, Shinki Oyabu, Mitsuyoshi Yamagishi and Katsuhiro Murata : A Systematic Study of Dust in Early-Type Galaxies with Akari, Publications of The Korean Astronomical Society, Vol.32, No.1, 151-153, 2017.
Shinki Oyabu, Hidehiro Kaneda, Masaya Izuhara, Keisuke Tomita, Daisuke Ishihara, Kimiaki Kawara and Yoshiki Matsuoka : Akari Observations of Dusty Tori of Active Galactic Nuclei, Publications of The Korean Astronomical Society, Vol.32, No.1, 157-161, 2017.
Mai Shirahata, Takao Nakagawa, Shinki Oyabu and Tomonori Usuda : Near-Infrared Spectroscopy of CO Ro-Vibrational Absorption Toward Heavily Obscured AGNs, Publications of The Korean Astronomical Society, Vol.32, No.1, 169-173, 2017.
Yoshiki Toba, Shinki Oyabu, Hideo Matsuhara, Daisuke Ishihara, A. Matt Malkan, Takehiko Wada, Youichi Ohyama, Hirokazu Kataza, Satoshi Takita and Chisato Yamauchi : Luminosity Dependence of the Covering Factor of the Dust Torus in Active Galactic Nuclei Revealed by Akari, Publications of The Korean Astronomical Society, Vol.32, No.1, 193-195, 2017.
Angel Castro, Takamitsu Miyaji, Mai Shirahata, Kohei Ichikawa, Shinki Oyabu, David Clark, Masatoshi Imanishi, Takao Nakagawa and Yoshihiro Ueda : AKARI Infrared Camera Observations of the 3.3 μm PAH Feature in Swift/BAT AGNs, Publications of The Korean Astronomical Society, Vol.32, No.1, 197-199, 2017.
H. Matsuhara, T. Wada, N. Oi, T. Takagi, T. Nakagawa, K. Murata, T. Goto, Shinki Oyabu, T. T. Takeuchi, K. Malek, A. Solarz, Y. Ohyama, T. Miyaji, M. Krumpe, M. H. Lee, M. Im, S. Serjeant, P. C. Pearson, J. G. White, A. M. Malkan, H. Hanami, T. Ishigaki, D. Burgarella, V. Buat and A. Pollo : Overview of North Ecliptic Pole Deep Multi-Wavelength Survey Nep-Deep, Publications of The Korean Astronomical Society, Vol.32, No.1, 213-217, 2017.
(要約)
The recent updates of the North Ecliptic Pole deep (0.5~deg2, NEP- Deep) multi-wavelength survey covering from X-ray to radio-wave is presented. The NEP-Deep provides us with several thousands of 15~$u$m or 18~$u$m selected sample of galaxies, which is the largest sample ever made at this wavelengths. A continuous filter coverage in the mid- infrared wavelength (7, 9, 11, 15, 18, and 24~$u$m) is unique and vital to diagnose the contributions from starbursts and AGNs in the galaxies out to $z$=2.The new goal of the project is to resolve the nature of the cosmic star formation history at the violent epoch (e.g. $z$=1--2), and to find a clue to understand its decline from $z$=1 to present universe by utilizing the unique power of the multi-wavelength survey. The progress in this context is briefly mentioned.
Tomotsugu Goto, Yoshiki Toba, Yousuke Utsumi, Nagisa Oi, Toshinobu Takagi, Matt Malkan, Youichi Ohayma, Kazumi Murata, Paul Price, Marios Karouzos, Hideo Matsuhara, Takao Nakagawa, Takehiko Wada, Steve Serjeant, Denis Burgarella, Veronique Buat, Masahiro Takada, Satoshi Miyazaki, Masamune Oguri, Takamitsu Miyaji, Shinki Oyabu, Glenn White, Tsutomu Takeuchi, Hanae Inami, Chris Perason, Katarzyna Malek, Lucia Marchetti, Mok Hyung Lee, Myung Im, Jin Seong Kim, Ekaterina Koptelova, Dani Chao, Yi-Han Wu, AKARI Survey NEP Team and AKARI Survey Sky All Team : Hyper Suprime-Camera Survey of the Akari NEP Wide Field, Publications of The Korean Astronomical Society, Vol.32, No.1, 225-230, 2017.
(要約)
The extragalactic background suggests half the energy generated by stars was reprocessed into the infrared (IR) by dust. At z ?1.3, 90% of star formation is obscured by dust. To fully understand the cosmic star formation history, it is critical to investigate infrared emission. AKARI has made deep mid-IR observation using its continuous 9-band filters in the NEP field (5.4 deg^2), using ?10% of the entire pointed observations available throughout its lifetime. However, there remain 11,000 AKARI infrared sources undetected with the previous CFHT/Megacam imaging (r ?25.9ABmag). Redshift and IR luminosity of these sources are unknown. These sources may contribute significantly to the cosmic star- formation rate density (CSFRD). For example, if they all lie at 1 < z < 2, the CSFRD will be twice as high at the epoch. We are carrying out deep imaging of the NEP field in 5 broad bands (g,r,i,z, and y) using Hyper Suprime-Camera (HSC), which has 1.5 deg field of view in diameter on Subaru 8m telescope. This will provide photometric redshift information, and thereby IR luminosity for the previously-undetected 11,000 faint AKARI IR sources. Combined with AKARI's mid-IR AGN/SF diagnosis, and accurate mid-IR luminosity measurement, this will allow a complete census of cosmic star-formation/AGN accretion history obscured by dust.
Chris Sedgwick, Stephen Serjeant, Chris Pearson, I. Yamamura, S. Makiuti, N. Ikeda, Y. Fukuda, Shinki Oyabu, T. Koga, S. Amber and J. Glenn White : Akari All-Sky Bright Source Catalogue: Far-Infrared Luminous Quasars and the Optical Far-Infrared Correlation, Publications of The Korean Astronomical Society, Vol.32, 305, 2017.
M. Yamagishi, H. Kaneda, D. Ishihara, Shinki Oyabu, T. Suzuki, T. Onaka, T. Nagayama, T. Umemoto, T. Minamidani, A. Nishimura, M. Matsuo, S. Fujita, Y. Tsuda, M. Kohno and S. Ohashi : Spatial Variations of PAH Properties in M17SW Revealed by Spitzer/IRS Spectral Mapping, The Astrophysical Journal, Vol.833, No.2, 163, 2016.
(要約)
We present Spitzer/IRS mid-infrared spectral maps of the Galactic star- forming region M17 as well as IRSF/SIRIUS Brγ and Nobeyama 45 m/FOREST 13CO (J = 1-0) maps. The spectra show prominent features due to polycyclic aromatic hydrocarbons (PAHs) at wavelengths of 6.2, 7.7, 8.6, 11.3, 12.0, 12.7, 13.5, and 14.2 μm. We find that the PAH emission features are bright in the region between the H II region traced by Brγ and the molecular cloud traced by 13CO, supporting that the PAH emission originates mostly from photo-dissociation regions. Based on the spatially resolved Spitzer/IRS maps, we examine spatial variations of the PAH properties in detail. As a result, we find that the interband ratio of PAH 7.7 μm/PAH 11.3 μm varies locally near M17SW, but rather independently of the distance from the OB stars in M17, suggesting that the degree of PAH ionization is mainly controlled by local conditions rather than the global UV environments determined by the OB stars in M17. We also find that the interband ratios of the PAH 12.0 μm, 12.7 μm, 13.5 μm, and 14.2 μm features to the PAH 11.3 μm feature are high near the M17 center, which suggests structural changes of PAHs through processing due to intense UV radiation, producing abundant edgy irregular PAHs near the M17 center.
Naoki Isobe, Taiki Kawamuro, Shinki Oyabu, Takao Nakagawa, Shunsuke Baba, Kenichi Yano, Yoshihiro Ueda and Yoshiki Toba : X-ray and infrared diagnostics of nearby active galactic nuclei with MAXI and AKARI, Publications of the Astronomical Society of Japan, Vol.68, No.6, 98, 2016.
(要約)
Nearby active galactic nuclei were diagnosed in the X-ray and mid-to-far infrared wavelengths with Monitor of All-sky X-ray Image (MAXI) and the Japanese infrared observatory AKARI, respectively. One hundred of the X-ray sources listed in the second release of the MAXI all-sky X-ray source catalog are currently identified as non-blazar-type active galactic nuclei. These include 95 Seyfert galaxies and 5 quasars, and they are composed of 73 type-1 and 27 type-2 objects. The AKARI all-sky survey point source catalog was searched for their mid- and far-infrared counterparts at 9, 18, and 90 μm. As a result, 69 Seyfert galaxies in the MAXI catalog (48 type-1 and 21 type-2) were found to be detected with AKARI. The X-ray (3-4 keV and 4-10 keV) and infrared luminosities of these objects were investigated, together with their color information. Adopting the canonical photon index, Γ = 1.9, of the intrinsic X-ray spectrum of the Seyfert galaxies, the X-ray hardness ratio between the 3-4 and 4-10 keV ranges derived with MAXI was roughly converted into the absorption column density. After the X-ray luminosity was corrected for absorption from the estimated column density, the well-known X-ray-to-infrared luminosity correlation was confirmed, at least in the Compton-thin regime. In contrast, NGC 1365, the only Compton-thick object in the MAXI catalog, was found to deviate from the correlation toward a significantly lower X-ray luminosity by nearly an order of magnitude. It was verified that the relation between the X-ray hardness below 10 keV and X-ray-to-infrared color acts as an effective tool to pick up Compton-thick objects. The difference in the infrared colors between the type-1 and type-2 Seyfert galaxies and its physical implication on the classification and unification of active galactic nuclei are briefly discussed.
(キーワード)
galaxies: active / galaxies: Seyfert / infrared: galaxies / X-rays: galaxies / Astrophysics - Astrophysics of Galaxies / Astrophysics - High Energy Astrophysical Phenomena
T. Wada, Y. Arai, S. Baba, M. Hanaoka, Y. Hattori, H. Ikeda, H. Kaneda, C. Kochi, A. Miyachi, K. Nagase, H. Nakaya, M. Ohno, Shinki Oyabu, T. Suzuki, S. Ukai, K. Watanabe and K. Yamamoto : Development for Germanium Blocked Impurity Band Far-Infrared Image Sensors with Fully-Depleted Silicon-On-Insulator CMOS Readout Integrated Circuit, Journal of Low Temperature Physics, Vol.184, 217-224, 2016.
(要約)
We are developing far-infrared (FIR) imaging sensors for low-background and high-sensitivity applications such as infrared astronomy. Previous FIR monolithic imaging sensors, such as an extrinsic germanium photo- conductor (Ge PC) with a PMOS readout integrated circuit (ROIC) hybridized by indium pixel-to-pixel interconnection, had three difficulties: (1) short cut-off wavelength (120 pmu m), (2) large power consumption (10 pmu W/pixel), and (3) large mismatch in thermal expansion between the Ge PC and the Si ROIC. In order to overcome these difficulties, we developed (1) a blocked impurity band detector fabricated by a surface- activated bond technology, whose cut-off wavelength is longer than 160 pmu m, (2) a fully-depleted silicon-on- insulator CMOS ROIC which works below 4 K with 1 pmu W/pixel operating power, and (3) a new concept, Si-supported Ge detector, which shows tolerance to thermal cycling down to 3 K. With these new techniques, we are now developing a 32 × 32 FIR imaging sensor.
M. Hanaoka, H. Kaneda, Shinki Oyabu, M. Yamagishi, Y. Hattori, S. Ukai, K. Shichi, T. Wada, T. Suzuki, K. Watanabe, K. Nagase, S. Baba and C. Kochi : Development of Blocked-Impurity-Band-Type Ge Detectors Fabricated with the Surface-Activated Wafer Bonding Method for Far-Infrared Astronomy, Journal of Low Temperature Physics, Vol.184, 225-230, 2016.
(要約)
We report the current status of the development of our new detectors for far-infrared (FIR) astronomy. We develop Blocked-Impurity-Band (BIB)-type Ge detectors to realize large-format compact arrays covering a wide FIR wavelength range up to 200 pmu m. We fabricated Ge junction devices of different physical parameters with a BIB-type structure, using the room temperature, surface-activated wafer bonding (SAB) method. We measured the absolute responsivity and the spectral response curve of each device at low temperatures, using an internal blackbody source in a cryostat and a Fourier transform spectrometer, respectively. The results show that the SAB Ge junction devices have significantly higher absolute responsivities and longer cut-off wavelengths of the spectral response than the conventional bulk Ge:Ga device. Based upon the results, we discuss the optimum parameters of SAB Ge junction devices for FIR detectors. We conclude that SAB Ge junction devices possess a promising applicability to next-generation FIR detectors covering wavelengths up to ? 200 pmu m with high responsivity. As a next step, we plan to fabricate a BIB-type Ge array device in combination with a low-power cryogenic readout integrated circuit.
Koichi Nagase, Takehiko Wada, Hirokazu Ikeda, Yasuo Arai, Morifumi Ohno, Misaki Hanaoka, Hidehiro Kanada, Shinki Oyabu, Yasuki Hattori, Sota Ukai, Toyoaki Suzuki, Kentaroh Watanabe, Shunsuke Baba, Chihiro Kochi and Keita Yamamoto : A Demonstration of TIA Using FD-SOI CMOS OPAMP for Far-Infrared Astronomy, Journal of Low Temperature Physics, Vol.184, 449-453, 2016.
(要約)
We are developing a fully depleted silicon-on-insulator (FD-SOI) CMOS readout integrated circuit (ROIC) operated at temperatures below ? 4 K. Its application is planned for the readout circuit of high-impedance far-infrared detectors for astronomical observations. We designed a trans-impedance amplifier (TIA) using a CMOS operational amplifier (OPAMP) with FD-SOI technique. The TIA is optimized to readout signals from a germanium blocked impurity band (Ge BIB) detector which is highly sensitive to wavelengths of up to ? 200 pmu m. For the first time, we demonstrated the FD-SOI CMOS OPAMP combined with the Ge BIB detector at 4.5 K. The result promises to solve issues faced by conventional cryogenic ROICs.
(キーワード)
Low temperature electronics / FD-SOI CMOS / Ge BIB detector
SMI (SPICA Mid-infrared Instrument) is one of the two focal-plane scientific instruments planned for new SPICA, and the Japanese instrument proposed and managed by a university consortium in Japan. SMI covers the wavelength range of 12 to 36 μm, using the following three spectroscopic channels with unprecedentedly high sensitivities: low- resolution spectroscopy (LRS; R = 50 - 120, 17 - 36 μm), mid-resolution spectroscopy (MRS; R = 1300 - 2300, 18 - 36 μm), and high-resolution spectroscopy (HRS; R = 28000, 12 - 18 μm). The key functions of these channels are high-speed dustband mapping with LRS, high-sensitivity multi-purpose spectral mapping with MRS, and high-resolution molecular- gas spectroscopy with HRS. This paper describes the technical concept and scientific capabilities of SMI.
Yuichi Terashima, Yoshitaka Hirata, Hisamitsu Awaki, Shinki Oyabu, Poshak Gandhi, Yoshiki Toba and Hideo Matsuhara : A New Sample of Obscured AGNs Selected from the XMM-Newton and AKARI Surveys, The Astrophysical Journal, Vol.814, No.1, 11, 2015.
(要約)
We report a new sample of obscured active galactic nuclei (AGNs) selected from the XMM-Newton serendipitous source and AKARI point-source catalogs. We match X-ray sources with infrared (18 and 90 μm) sources located at | b| t 10circ to create a sample consisting of 173 objects. Their optical classifications and absorption column densities measured by X-ray spectra are compiled and study efficient selection criteria to find obscured AGNs. We apply the criteria (1) X-ray hardness ratio defined by using the 2-4.5 keV and 4.5-12 keV bands > -0.1 and (2) EPIC-PN count rate (CR) in the 0.2-12 keV to infrared flux ratio CR/{F}90t 0.1 or CR/{F}18t 1, where F18 and F90 are infrared fluxes at 18 and 90 μm in Jy, respectively, to search for obscured AGNs. X-ray spectra of 48 candidates, for which no X-ray results have been published, are analyzed and X-ray evidence for the presence of obscured AGNs such as a convex shape X-ray spectrum indicative of absorption of {N}{{H}} ? 1022-24 cm-2, a very flat continuum, or a strong Fe-K emission line with an equivalent width of t 700 {{eV}} is found in 26 objects. Six of them are classified as Compton-thick AGNs, and four are represented by either Compton-thin or Compton-thick spectral models. The success rate of finding obscured AGNs combining our analysis and the literature is 92% if the 18 μm condition is used. Of the 26 objects, 4 are optically classified as an H ii nucleus and are new ``elusive AGNs'' in which star formation activity likely overwhelms AGN emission in the optical and infrared bands.
(キーワード)
galaxies: active / infrared: galaxies / X-rays: galaxies / Astrophysics - Astrophysics of Galaxies
A. Solarz, A. Pollo, T. T. Takeuchi, K. Małek, H. Matsuhara, J. G. White, A. P?piak, T. Goto, T. Wada, Shinki Oyabu, T. Takagi, Y. Ohyama, P. C. Pearson, H. Hanami, T. Ishigaki and M. Malkan : Clustering of the AKARI NEP deep field 24 μm selected galaxies, Astronomy & Astrophysics, Vol.582, A58, 2015.
(要約)
Aims: We present a method of selection of 24 μm galaxies from the AKARI north ecliptic pole (NEP) deep field down to 150 μJy and measurements of their two-point correlation function. We aim to associate various 24 μm selected galaxy populations with present day galaxies and to investigate the impact of their environment on the direction of their subsequent evolution. Methods: We discuss using of Support Vector Machines (SVM) algorithm applied to infrared photometric data to perform star-galaxy separation, in which we achieve an accuracy higher than 80%. The photometric redshift information, obtained through the CIGALE code, is used to explore the redshift dependence of the correlation function parameter (r0) as well as the linear bias evolution. This parameter relates galaxy distribution to the one of the underlying dark matter. We connect the investigated sources to their potential local descendants through a simplified model of the clustering evolution without interactions. Results: We observe two different populations of star-forming galaxies, at zmed ~ 0.25, zmed ~ 0.9. Measurements of total infrared luminosities (LTIR) show that the sample at zmed ~ 0.25 is composed mostly of local star-forming galaxies, while the sample at zmed ~ 0.9 is composed of luminous infrared galaxies (LIRGs) with LTIR ~ 1011.62 L?. We find that dark halo mass is not necessarily correlated with the LTIR: for subsamples with LTIR = 1011.15 L? at zmed ~ 0.7 we observe a higher clustering length (r0 = 6.21 ± 0.78[ h-1Mpc ]) than for a subsample with mean LTIR = 1011.84 L? at zmed ~ 1.1 (r0 = 5.86 ± 0.69h-1Mpc). We find that galaxies at zmed ~ 0.9 can be ancestors of present day L? early type galaxies, which exhibit a very high r0 ~ 8h-1 Mpc.
(キーワード)
infrared: galaxies / galaxies: statistics / galaxies: fundamental parameters / Astrophysics - Astrophysics of Galaxies / Astrophysics - Cosmology and Nongalactic Astrophysics
Yoshiki Toba, Tohru Nagao, A. Michael Strauss, Kentaro Aoki, Tomotsugu Goto, Masatoshi Imanishi, Toshihiro Kawaguchi, Yuichi Terashima, Yoshihiro Ueda, James Bosch, Kevin Bundy, Yoshiyuki Doi, Hanae Inami, Yutaka Komiyama, H. Robert Lupton, Hideo Matsuhara, Yoshiki Matsuoka, Satoshi Miyazaki, Tomoki Morokuma, Fumiaki Nakata, Nagisa Oi, Masafusa Onoue, Shinki Oyabu, Paul Price, J. Philip Tait, Tadafumi Takata, M. Manobu Tanaka, Tsuyoshi Terai, L. Edwin Turner, Tomohisa Uchida, Tomonori Usuda, Yousuke Utsumi, Yoshihiko Yamada and Shiang-Yu Wang : Hyper-luminous dust-obscured galaxies discovered by the Hyper Suprime-Cam on Subaru and WISE, Publications of the Astronomical Society of Japan, Vol.67, No.5, 86, 2015.
(要約)
We present the photometric properties of a sample of infrared (IR) bright dust-obscured galaxies (DOGs). Combining wide and deep optical images obtained with the Hyper Suprime-Cam on the Subaru Telescope and all-sky mid-IR (MIR) images taken with Wide-Field Infrared Survey Explorer, we discovered 48 DOGs with i - Ks > 1.2 and i - [22] > 7.0, where i, Ks, and [22] represent AB magnitude in the i-band, Ks-band, and 22 μm, respectively, in the GAMA 14 hr field (? 9 deg2). Among these objects, 31 (? 65%) show power-law spectral energy distributions (SEDs) in the near-IR (NIR) and MIR regime, while the remainder show an NIR bump in their SEDs. Assuming that the redshift distribution for our DOGs sample is Gaussian, with mean and sigma z = 1.99 ± 0.45, we calculated their total IR luminosity using an empirical relation between 22 μm luminosity and total IR luminosity. The average value of the total IR luminosity is (3.5 ± 1.1) × 1013 L?, which classifies them as hyper-luminous infrared galaxies. We also derived the total IR luminosity function (LF) and IR luminosity density (LD) for a flux-limited subsample of 18 DOGs with 22 μm flux greater than 3.0 mJy and with i-band magnitude brighter than 24 AB magnitude. The derived space density for this subsample is log φ = -6.59 ± 0.11 [Mpc-3]. The IR LF for DOGs including data obtained from the literature is fitted well by a double-power law. The derived lower limit for the IR LD for our sample is ϱIR ? 3.8 × 107 [L? Mpc-3] and its contributions to the total IR LD, IR LD of all ultra-luminous infrared galaxies, and that of all DOGs are > 3%, > 9%, and > 15%, respectively.
(キーワード)
catalogs / galaxies: active / galaxies: luminosity function / mass function / infrared: galaxies / methods: statistical / Astrophysics - Astrophysics of Galaxies
S. Oseki, Shinki Oyabu, D. Ishihara, K. Enya, K. Haze, T. Kotani, H. Kaneda, M. Nishiyama, L. Abe and T. Yamamuro : Coronagraphic Demonstration Experiment Using Aluminum Mirrors for Space Infrared Astronomical Observations, Publications of the Astronomical Society of the Pacific, Vol.127, No.956, 1077, 2015.
(要約)
For future space infrared astronomical coronagraphy, we perform experimental studies on the application of aluminum mirrors to a coronagraph. Cooled reflective optics is required for broad-band mid- infrared observations in space, while high-precision optics is required for coronagraphy. For the coronagraph instrument originally proposed for the next-generation infrared astronomical satellite project SPICA (SCI: SPICA Coronagraph Instrument), we fabricated and evaluated the optics consisting of high-precision aluminum off-axis mirrors with diamond- turned surfaces, and conducted a coronagraphic demonstration experiment using the optics with a coronagraph mask. We first measured the wave front errors (WFEs) of the aluminum mirrors with a He-Ne Fizeau interferometer to confirm that the power spectral densities of the WFEs satisfy the SCI requirements. Then we integrated the mirrors into an optical system and evaluated the overall performance of the system. As a result, we estimate the total WFE of the optics to be 33 nm (rms), each mirror contributing 10-20 nm (rms) for the central 14 mm area of the optics, and obtain a contrast of 10-5.4 as a coronagraph in the visible light. At a wavelength of 5 um, the coronagraphic system is expected to achieve a contrast of ~10-7 based on our model calculation with the measured optical performance. Thus our experiment demonstrates that aluminum mirror optics is applicable to a highly WFE- sensitive instrument such as a coronagraph in space.
(キーワード)
Astrophysics - Instrumentation and Methods for Astrophysics
M. Yamagishi, H. Kaneda, D. Ishihara, Shinki Oyabu, T. Onaka, T. Shimonishi and T. Suzuki : Systematic Variations in CO2/H2O Ice Abundance Ratios in Nearby Galaxies Found with AKARI Near-infrared Spectroscopy, The Astrophysical Journal, Vol.807, No.1, 29, 2015.
(要約)
We report CO2/H2O ice abundance ratios in seven nearby star-forming galaxies based on the AKARI near-infrared (2.5-5.0 μm) spectra. The CO2/H2O ice abundance ratios show clear variations between 0.05 and 0.2 with the averaged value of 0.14 ± 0.01. The previous study on M82 revealed that the CO2/H2O ice abundance ratios strongly correlate with the intensity ratios of the hydrogen recombination Brα line to the polycyclic aromatic hydrocarbon (PAH) 3.3 μm feature. In the present study, however, we find no correlation for the seven galaxies as a whole due to systematic differences in the relation between CO2/H2O ice abundance and Brα/PAH 3.3 μm intensity ratios from galaxy to galaxy. This result suggests that there is another parameter that determines the CO2/H2O ice abundance ratios in a galaxy in addition to the Brα/PAH 3.3 μm ratios. We find that the CO2/H2O ice abundance ratios positively correlate with the specific star formation rates of the galaxies. From these results, we conclude that CO2/H2O ice abundance ratios tend to be high in young star-forming galaxies.
(キーワード)
galaxies: individual: M77 / M82 / NGC 253 / NGC 1808 / NGC 3256 / Centaurus A / Circinus / galaxies: ISM / infrared: galaxies / ISM: molecules
Dohyeong Kim, Myungshin Im, Hoon Ji Kim, David Hyunsung Jun, Jong-Hak Woo, Mok Hyung Lee, Gyoon Myung Lee, Takao Nakagawa, Hideo Matsuhara, Takehiko Wada, Shinki Oyabu, Toshinobu Takagi, Youichi Ohyama and Seong-Kook Lee : The AKARI 2.5-5.0 μm Spectral Atlas of Type-1 Active Galactic Nuclei: Black Hole Mass Estimator, Line Ratio, and Hot Dust Temperature, The Astrophysical Journal. Supplement Series, Vol.216, No.1, 17, 2015.
(要約)
We present 2.5-5.0 μm spectra of 83 nearby (0.002 < z < 0.48) and bright (K < 14 mag) type-1 active galactic nuclei (AGNs) taken with the Infrared Camera on board AKARI. The 2.5-5.0 μm spectral region contains emission lines such as Brβ (2.63 μm), Brα (4.05 μm), and polycyclic aromatic hydrocarbons (3.3 μm), which can be used for studying the black hole (BH) masses and star formation activity in the host galaxies of AGNs. The spectral region also suffers less dust extinction than in the ultra violet (UV) or optical wavelengths, which may provide an unobscured view of dusty AGNs. Our sample is selected from bright quasar surveys of Palomar-Green and SNUQSO, and AGNs with reverberation-mapped BH masses from Peterson et al. Using 11 AGNs with reliable detection of Brackett lines, we derive the Brackett-line-based BH mass estimators. We also find that the observed Brackett line ratios can be explained with the commonly adopted physical conditions of the broad line region. Moreover, we fit the hot and warm dust components of the dust torus by adding photometric data of SDSS, 2MASS, WISE, and ISO to the AKARI spectra, finding hot and warm dust temperatures of ~1100 K and ~220 K, respectively, rather than the commonly cited hot dust temperature of 1500 K.
(キーワード)
galaxies: active / galaxies: nuclei / infrared: galaxies / quasars: emission lines / quasars: general / Astrophysics - Astrophysics of Galaxies
Angel Castro, Takamitsu Miyaji, Mai Shirahata, Kohei Ichikawa, Shinki Oyabu, M. David Clark, Masatoshi Imanishi, Takao Nakagawa and Yoshihiro Ueda : AKARI infrared camera observations of the 3.3 μm PAH feature in Swift/BAT AGNs, Publications of the Astronomical Society of Japan, Vol.66, No.6, 110, 2014.
(要約)
We explore the relationships between the 3.3 μm polycyclic aromatic hydrocarbon (PAH) feature and active galactic nucleus (AGN) properties of a sample of 54 hard X-ray selected bright AGNs, including both Seyfert 1 and Seyfert 2 type objects, using the InfraRed Camera (IRC) on board the infrared astronomical satellite AKARI. The sample is selected from the nine-month Swift/BAT survey in the 14-195 keV band and all of them have measured X-ray spectra at E ? 10 keV. These X-ray spectra provide measurements of the neutral hydrogen column density (NH) towards the AGNs. We use the 3.3 μm PAH luminosity (L3.3μm) as a proxy for star-formation activity and hard X-ray luminosity (L14-195 keV) as an indicator of the AGN activity. We search for possible differences in star-formation activity between type 1 (unabsorbed) and type 2 (absorbed) AGNs. We have made several statistical analyses taking the upper limits of the PAH lines into account utilizing survival analysis methods. The results of our log (L14-195 keV) versus log (L3.3 μm) regression show a positive correlation and the slope for the type 1/unobscured AGNs is steeper than that of type 2/obscured AGNs at a 3 ς level. Our analysis also shows that the circumnuclear star formation is more enhanced in type 2/absorbed AGNs than type 1/unabsorbed AGNs for low X-ray luminosity/low Eddington ratio AGNs, while there is no significant dependence of star-formation activities on the AGN type in the high X-ray luminosities/Eddington ratios.
(キーワード)
galaxies: active / galaxies: Seyfert / X-rays: galaxies / Astrophysics - Astrophysics of Galaxies
Kohei Ichikawa, Masatoshi Imanishi, Yoshihiro Ueda, Takao Nakagawa, Mai Shirahata, Hidehiro Kaneda and Shinki Oyabu : AKARI IRC 2.5-5 μm Spectroscopy of Infrared Galaxies over a Wide Luminosity Range, The Astrophysical Journal, Vol.794, No.2, 139, 2014.
(要約)
We present the result of a systematic infrared 2.5-5 μm spectroscopic study of 22 nearby infrared galaxies over a wide infrared luminosity range (1010 L ? < L IR < 1013 L ?) obtained from the AKARI Infrared Camera (IRC). The unique band of the AKARI IRC spectroscopy enables us to access both the 3.3 μm polycyclic aromatic hydrocarbon (PAH) emission feature from star-forming activity and the continuum of torus-dust emission heated by an active galactic nucleus (AGN). Applying our AGN diagnostics to the AKARI spectra, we discover 14 buried AGNs. The large fraction of buried AGNs suggests that AGN activity behind the dust is almost ubiquitous in ultra-/luminous infrared galaxies (U/LIRGs). We also find that both the fraction and energy contribution of buried AGNs increase with infrared luminosity from 1010 L ? to 1013 L ?, including normal infrared galaxies with L IR < 1011 L ?. The energy contribution from AGNs in the total infrared luminosity is only ~7% in LIRGs and ~20% in ULIRGs, suggesting that the majority of the infrared luminosity originates from starburst activity. Using the PAH emission, we investigate the luminosity relation between star formation and AGNs. We find that these infrared galaxies exhibit higher star formation rates than optically selected Seyfert galaxies with the same AGN luminosities, implying that infrared galaxies could be an early evolutionary phase of AGN.
(キーワード)
galaxies: active / galaxies: nuclei / infrared: galaxies / Astrophysics - Astrophysics of Galaxies / Astrophysics - Cosmology and Nongalactic Astrophysics
P. Chris Pearson, S. Serjeant, Shinki Oyabu, H. Matsuhara, T. Wada, T. Goto, T. Takagi, M. H. Lee, M. Im, Y. Ohyama, J. S. Kim and K. Murata : The first source counts at 18 μm from the AKARI NEP Survey, Monthly Notices of the Royal Astronomical Society, Vol.444, No.1, 846-859, 2014.
(要約)
We present the first galaxy counts at 18 μm using the Japanese AKARI satellite's survey at the North Ecliptic Pole (NEP), produced from the images from the NEP-Deep and NEP-Wide surveys covering 0.6 and 5.8 deg2, respectively. We describe a procedure using a point source filtering algorithm to remove background structure and a minimum variance method for our source extraction and photometry that delivers the optimum signal to noise for our extracted sources, confirming this by comparison with standard photometry methods. The final source counts are complete and reliable over three orders of magnitude in flux density, resulting in sensitivities (80 per cent completeness) of 0.15 and 0.3 mJy for the NEP-Deep and NEP-Wide surveys, respectively, a factor of 1.3 deeper than previous catalogues constructed from this field. The differential source counts exhibit a characteristic upturn from Euclidean expectations at around a milliJansky and a corresponding evolutionary bump between 0.2-0.4 mJy consistent with previous mid- infrared surveys with ISO and Spitzer at 15 and 24 μm. We compare our results with galaxy evolution models confirming the striking divergence from the non-evolving scenario. The models and observations are in broad agreement implying that the source counts are consistent with a strongly evolving population of luminous infrared galaxies at redshifts higher than unity. Integrating our source counts down to the limit of the NEP survey at the 150 μJy level we calculate that AKARI has resolved approximately 55 per cent of the 18 μm cosmic infrared background relative to the predictions of contemporary source count models.
(キーワード)
galaxies: evolution / infrared: galaxies / Astrophysics - Astrophysics of Galaxies / Astrophysics - Cosmology and Nongalactic Astrophysics / Astrophysics - Instrumentation and Methods for Astrophysics
H. Kaneda, D. Ishihara, K. Kobata, T. Kondo, Shinki Oyabu, R. Yamada, M. Yamagishi, T. Onaka and T. Suzuki : AKARI observations of interstellar dust grains in our Galaxy and nearby galaxies, Planetary and Space Science, Vol.100, 6-11, 2014.
(要約)
The infrared (IR) emission from interstellar dust grains is a powerful tool to trace star-formation activities in galaxies. Beyond such star- formation tracers, spectral information on polycyclic aromatic hydrocarbons (PAHs) and large grains, or even their photometric intensity ratios, has deep physical implications for understanding the properties of the interstellar medium. With the AKARI satellite launched in 2006, we have performed a systematic study of interstellar dust grains in various environments of galaxies including our Galaxy. Because of its unique capabilities, such as mid-/far-IR all-sky surveys and near -/far-IR spectroscopy, AKARI has provided new knowledge on the processing of dust, particularly carbonaceous grains including PAHs, in the interstellar space. For example, the near-IR spectroscopy has revealed structural changes of hydrocarbon grains in harsh environments of galaxies. In this paper, we focus on the properties of the PAH emission obtained by the AKARI mid-IR all-sky survey and near-IR spectroscopy.
Y. Toba, Shinki Oyabu, H. Matsuhara, A. M. Malkan, P. Gandhi, T. Nakagawa, N. Isobe, M. Shirahata, N. Oi, Y. Ohyama, S. Takita, C. Yamauchi and K. Yano : Luminosity and Redshift Dependence of the Covering Factor of Active Galactic Nuclei viewed with WISE and Sloan Digital Sky Survey, The Astrophysical Journal, Vol.788, No.1, 45, 2014.
(要約)
In this work, we investigate the dependence of the covering factor (CF) of active galactic nuclei (AGNs) on the mid-infrared (MIR) luminosity and the redshift. We constructed 12 and 22 μm luminosity functions (LFs) at 0.006 <=z <= 0.3 using Wide-field Infrared Survey Explorer (WISE) data. Combining the WISE catalog with Sloan Digital Sky Survey (SDSS) spectroscopic data, we selected 223,982 galaxies at 12 μm and 25,721 galaxies at 22 μm for spectroscopic classification. We then identified 16,355 AGNs at 12 μm and 4683 AGNs at 22 μm by their optical emission lines and cataloged classifications in the SDSS. Following that, we estimated the CF as the fraction of Type 2 AGN in all AGNs whose MIR emissions are dominated by the active nucleus (not their host galaxies) based on their MIR colors. We found that the CF decreased with increasing MIR luminosity, regardless of the choice of Type 2 AGN classification criteria, and the CF did not change significantly with redshift for z <= 0.2. Furthermore, we carried out various tests to determine the influence of selection bias and confirmed that similar dependences exist, even when taking these uncertainties into account. The luminosity dependence of the CF can be explained by the receding torus model, but the "modified" receding torus model gives a slightly better fit, as suggested by Simpson.
(キーワード)
catalogs / galaxies: active / galaxies: luminosity function / mass function / galaxies: nuclei / infrared: galaxies / methods: statistical / Astrophysics - Astrophysics of Galaxies
Y. Urazuka, Shinki Oyabu, H. Chen, B. Peng, H. Otsuki, T. Tanaka and K. Matsuyama : Spin wave based parallel logic operations for binary data coded with domain walls, Journal of Applied Physics, Vol.115, No.17, 17D505, 2014.
(要約)
We numerically investigate the feasibility of spin wave (SW) based parallel logic operations, where the phase of SW packet (SWP) is exploited as a state variable and the phase shift caused by the interaction with domain wall (DW) is utilized as a logic inversion functionality. A designed functional element consists of parallel ferromagnetic nanowires (6 nm-thick, 36 nm-width, 5120 nm-length, and 200 nm separation) with the perpendicular magnetization and sub-μm scale overlaid conductors. The logic outputs for binary data, coded with the existence ("1") or absence ("0") of the DW, are inductively read out from interferometric aspect of the superposed SWPs, one of them propagating through the stored data area. A practical exclusive-or operation, based on 2ϖ periodicity in the phase logic, is demonstrated for the individual nanowire with an order of different output voltage Vout, depending on the logic output for the stored data. The inductive output from the two nanowires exhibits well defined three different signal levels, corresponding to the information distance (Hamming distance) between 2-bit data stored in the multiple nanowires.
K. Murata, H. Matsuhara, T. Wada, K. Arimatsu, N. Oi, T. Takagi, Shinki Oyabu, T. Goto, Y. Ohyama, M. Malkan, C. Pearson, K. Ma?ek and A. Solarz : AKARI North Ecliptic Pole Deep Survey. Revision of the catalogue via a new image analysis, Astronomy & Astrophysics, Vol.559, A132, 2013.
(要約)
Context. We present the revised near- to mid-infrared catalogue of the AKARI North Ecliptic Pole deep survey. The survey has the unique advantage of continuous filter coverage from 2 to 24 μm over nine photometric bands, but the initial version of the survey catalogue leaves room for improvement in the image analysis stage; the original images are strongly contaminated by the behaviour of the detector and the optical system. Aims: The purpose of this study is to devise new image analysis methods and to improve the detection limit and reliability of the source extraction. Methods: We removed the scattered light and stray light from the Earth limb, and corrected for artificial patterns in the images by creating appropriate templates. We also removed any artificial sources due to bright sources by using their properties or masked them out visually. In addition, for the mid- infrared source extraction, we created detection images by stacking all six bands. This reduced the sky noise and enabled us to detect fainter sources more reliably. For the near-infrared source catalogue, we considered only objects with counterparts from ground-based catalogues to avoid fake sources. For our ground-based catalogues, we used catalogues based on the CFHT/MegaCam z' band, CFHT/WIRCam Ks band and Subaru/Scam z' band. Objects with multiple counterparts were all listed in the catalogue with a merged flag for the AKARI flux. Results: The detection limits of all mid-infrared bands were improved by ~20%, and the total number of detected objects was increased by ~2000 compared with the previous version of the catalogue; it now has 9560 objects. The 5ς detection limits in our catalogue are 11, 9, 10, 30, 34, 57, 87, 93, and 256 μJy in the N2, N3, N4, S7, S9W, S11, L15, L18W, and L24 bands, respectively. The astrometric accuracies of these band detections are 0.48, 0.52, 0.55, 0.99, 0.95, 1.1, 1.2, 1.3, and 1.6 arcsec, respectively. The false-detection rate of all nine bands was decreased to less than 0.3%. In total, 27 770 objects are listed in the catalogue, 11 349 of which have mid-infrared fluxes. The catalogue is available at the CDS via anonymous ftp to http://cdsarc.u-strasbg.fr (ftp://130.79.128.5) or via http://cdsarc.u-strasbg.fr/viz- bin/qcat?J/A+A/559/A132 or at the ISAS/JAXA observers page, http://www.ir.isas.jax a.jp/ASTRO-F/Observation/
(キーワード)
methods: data analysis / infrared: galaxies / surveys / catalogs
D. Ishihara, H. Kaneda, Shinki Oyabu, T. Kondo, M. Yamagishi and A. Yasuda : AKARI Observations of Interstellar Polycyclic Aromatic Hydrocarbons, International Astrobiology Workshop 2013, Vol.1766, 1048, 2013.
(要約)
We review the results from AKARI observations of PAHs. We also discuss our future prospect for this study using the next Japan-led infrared space mission, SPICA.
66.
Chris Sedgwick, Stephen Serjeant, Chris Pearson, Ian Smail, Myungshin Im, Shinki Oyabu, Toshinobu Takagi, Hideo Matsuhara, Takehiko Wada, Mok Hyung Lee, Woong-Seob Jeong and J. Glenn White : Detection of Hα emission from z > 3.5 submillimetre luminous galaxies with AKARI-FUHYU spectroscopy, Monthly Notices of the Royal Astronomical Society, Vol.436, No.1, 395-400, 2013.
(要約)
We present tentative Hα emission line detections of four submillimetre- detected galaxies at z > 3.5: the radio galaxies 8C1909+722 and 4C60.07 at signal-to-noise ratios (SNRs) of 3.1 and 2.5, and two submillimetre-selected galaxies (SMGs) near the first of these at SNRs of 10.0 and 2.4, made with the AKARI space telescope as part of the Follow-Up Hayai-Yasui-Umai mission programme. These are the highest redshift Hα detections in such galaxies, made possible by AKARI's unique near-infrared spectroscopic capability. The two radio galaxies had known redshifts and surrounding structure, and we have detected broad Hα components indicating the presence of dust-shrouded quasars. We conclude that powerful active galactic nuclei (AGNs) at z > 3.5 occur in peaks of the star formation density fields, supporting a close connection between stellar mass build-up and black hole mass assembly at this redshift. We also show that 4C60.07 is a binary AGN. The Hα detections of the two SMGs are the first redshift determinations for these sources, confirming their physical association around their companion radio galaxy. The Hα-derived star formation rates (SFRs) for the SMGs are lower than their far-infrared derived SFRs by a factor of ?10, suggesting a level of dust obscuration similar to that found in studies at ?1 < z < 2.7.
(キーワード)
galaxies: active / galaxies: evolution / galaxies: starburst / galaxies: star formation / infrared: galaxies / Astrophysics - Cosmology and Nongalactic Astrophysics
S. Serjeant, M. Negrello, C. Pearson, A. Mortier, J. Austermann, I. Aretxaga, D. Clements, S. Chapman, S. Dye, J. Dunlop, L. Dunne, D. Farrah, D. Hughes, M. H. Lee, H. Matsuhara, E. Ibar, M. Im, -S. W. Jeong, S. Kim, Shinki Oyabu, T. Takagi, T. Wada, G. Wilson, M. Vaccari and M. Yun : VizieR Online Data Catalog: AGNs in submm-selected Lockman Hole galaxies (Serjeant+, 2010), VizieR Online Data Catalog, J/A+A/514/A10, 2013.
(要約)
We present a comparison of the SCUBA half degree extragalactic survey (SHADES) at 450μm, 850μm and 1100μm with deep guaranteed time 15μm AKARI FU-HYU survey data and Spitzer guaranteed time data at 3.6-24μm in the Lockman hole east. The AKARI data was analysed using bespoke software based in part on the drizzling and minimum-variance matched filtering developed for SHADES, and was cross-calibrated against ISO fluxes. (2 data files).
(キーワード)
Active gal. nuclei / Photometry: millimetric/submm / Energy distributions
68.
A. Pollo, T. T. Takeuchi, A. Solarz, P. Rybka, L. T. Suzuki, A. Pȩpiak and Shinki Oyabu : Clustering of far-infrared galaxies in the AKARI All-Sky Survey North, Earth, Planets and Space, Vol.65, 1109, 2013.
(要約)
We present the measurements of the angular two-point correlation function for AKARI 90-μm point sources, detected outside the Milky Way plane and other regions characterized by high Galactic extinction in the northern Galactic hemisphere, and categorized as extragalactic sources according to our far-infrared-color based criterion. Together with our previous work (Pollo et al., 2013) this is the first measurement of the large-scale angular clustering of galaxies selected in the far-infrared after IRAS. We present the first attempt to estimate the spatial clustering properties of AKARI All-Sky galaxies and we conclude that they are mostly a very nearby ( z ? 0.1) population of moderately clustered galaxies. We measure their correlation length r 0 ~ 4.5 h -1 Mpc, which is consistent with the assumption that the FIS AKARI All-Sky surveys observes mostly a nearby star-forming population of galaxies.
Rika Yamada, Shinki Oyabu, Hidehiro Kaneda, Mitsuyoshi Yamagishi, Daisuke Ishihara, Hoon Ji Kim and Myungshin Im : A Relation of the PAH 3.3 μm Feature with Star-forming Activity for Galaxies with a Wide Range of Infrared Luminosity, Publications of the Astronomical Society of Japan, Vol.65, No.5, 103, 2013.
(要約)
For star-forming galaxies, we investigated a global relation between the polycyclic aromatic hydrocarbon (PAH) emission luminosity at 3.3 μm, LPAH3.3, and the infrared (8-1000 μm) luminosity, LIR, to understand how the PAH 3.3 μm feature relates to star-formation activity. With AKARI, we performed near-infrared (2.5-5 μm) spectroscopy of 184 galaxies having LIR ? 108-1013 L?. We classified the samples into infrared galaxies (IRGs: LIR < 1011 L?), luminous infrared galaxies (LIRGs: LIR ? 1011 -1012 L?) and ultra-luminous infrared galaxies (ULIRGs: LIR > 1012 L?). We excluded sources likely to be contaminated by AGN activity, based on the rest-frame equivalent width of the PAH emission feature (< 40 nm) and the power-law index, representing the slope of continuum emission (Γ > 1 Fν ∝ λΓ). Of these samples, 13 IRGs, 67 LIRGs, and 20 ULIRGs show the PAH emission feature at λ rest = 3.3 μm in their spectra. We find that the LPAH3.3/LIR ratio considerably decreases toward the luminous end. Utilizing the mass and temperature of dust grains as well as the Brα emission for the galaxies, we discuss the cause of the relative decrease in the PAH emission with LIR.
(キーワード)
galaxies: active / galaxies: starburst / infrared: galaxies / Astrophysics - Cosmology and Nongalactic Astrophysics
Yoshiki Toba, Shinki Oyabu, Hideo Matsuhara, A. Matthew Malkan, Daisuke Ishihara, Takehiko Wada, Youichi Ohyama, Satoshi Takita and Chisato Yamauchi : The 9 and 18 Micrometer Luminosity Functions of Various Types of Galaxies with AKARI: Implication for the Dust Torus Structure of AGN, Publications of the Astronomical Society of Japan, Vol.65, No.5, 113, 2013.
(要約)
We present the 9 and 18 μm luminosity functions (LFs) of galaxies at 0.006 ? z ? 0.8 (with an average redshift of ? 0.04) using the AKARI mid-infrared all-sky survey catalog. We selected 243 galaxies at 9 μm and 255 galaxies at 18 μm from the Sloan Digital Sky Survey (SDSS) spectroscopy region. These galaxies were then classified by their optical emission lines, such as the line width of Hα or by their emission line ratios of [O III]/Hβ and [N II]/Hα into five types: Type 1 active galactic nuclei (AGN) (Type 1); Type 2 AGN (Type 2); low- ionization narrow emission line galaxies (LINER); galaxies with both star formation and narrow-line AGN activity (composite galaxies); and star-forming galaxies (SF). We found that (i) the number density ratio of Type 2 to Type 1 AGNs is 1.73 ± 0.36, which is larger than a result obtained from the optical LF and (ii) this ratio decreases with increasing 18 μ m luminosity.
(キーワード)
galaxies: active / galaxies: luminosity function / mass function / galaxies: nuclei / infrared: galaxies / Astrophysics - Cosmology and Nongalactic Astrophysics
Mitsuyoshi Yamagishi, Hidehiro Kaneda, Daisuke Ishihara, Shinki Oyabu, Takashi Onaka, Takashi Shimonishi, Toyoaki Suzuki and Chol Young Minh : Difference in the Spatial Distribution between H2O and CO2 Ices in M 82 Found with AKARI, The Astrophysical Journal, Vol.773, No.2, L37, 2013.
(要約)
With AKARI, we obtain the spatially resolved near-infrared (NIR) (2.5-5.0 μm) spectra for the nearby starburst galaxy M 82. These spectra clearly show absorption features due to interstellar ices. Based on the spectra, we created the column density maps of H2O and CO2 ices. As a result, we find that the spatial distribution of H2O ice is significantly different from that of CO2 ice; H2O ice is widely distributed, while CO2 ice is concentrated near the galactic center. Our result reveals for the first time variations in CO2/H2O ice abundance ratio on a galactic scale, suggesting that an ice-forming interstellar environment changes within a galaxy. We discuss the cause of the spatial variations in the ice abundance ratio, utilizing spectral information on the hydrogen recombination Brα and Brβ lines and the polycyclic aromatic hydrocarbon 3.3 μm emission appearing in the AKARI NIR spectra.
(キーワード)
galaxies: individual: M 82 / galaxies: ISM / infrared: galaxies / ISM: molecules / Astrophysics - Astrophysics of Galaxies
N. Ienaka, K. Kawara, Y. Matsuoka, H. Sameshima, Shinki Oyabu, T. Tsujimoto and A. B. Peterson : Diffuse Galactic Light in the Field of the Translucent High Galactic Latitude Cloud MBM32, The Astrophysical Journal, Vol.767, No.1, 80, 2013.
(要約)
We have conducted B-, g-, V-, and R-band imaging in a 45' × 40' field containing part of the high Galactic latitude translucent cloud MBM32, and correlated the intensity of diffuse optical light S ν(λ) with that of 100 μm emission S ν(100 μm). A χ2 minimum analysis is applied to fit a linear function to the measured correlation and derive the slope parameter b(λ) = ?S ν(λ)/?S ν(100 μm) of the best-fit linear function. Compiling a sample by combining our b(λ) and published ones, we show that the b(λ) strength varies from cloud to cloud by a factor of four. Finding that b(λ) decreases as S ν(100 μm) increases in the sample, we suggest that a nonlinear correlation including a quadratic term of S ν(100 μm)2 should be fitted to the measured correlation. The variation of optical depth, which is AV = 0.16-2.0 in the sample, can change b(λ) by a factor of 2-3. There would be some contribution to the large b(λ) variation from the forward- scattering characteristic of dust grains which is coupled to the non- isotropic interstellar radiation field (ISRF). Models of the scattering of diffuse Galactic light (DGL) underestimate the b(λ) values by a factor of two. This could be reconciled by deficiency in UV photons in the ISRF or by a moderate increase in dust albedo. Our b(λ) spectrum favors a contribution from extended red emission (ERE) to the diffuse optical light; b(λ) rises from B to V faster than the models, seems to peak around 6000 ? and decreases toward long wavelengths. Such a characteristic is expected from the models in which the DGL is combined with ERE.
A. Pollo, T. T. Takeuchi, L. T. Suzuki and Shinki Oyabu : Clustering of far-infrared galaxies in the AKARI All-Sky Survey, Earth, Planets and Space, Vol.65, 273, 2013.
(要約)
We present the first measurement of the angular two-point correlation function for AKARI 90-μm point sources, detected outside of the Milky Way plane and other regions characterized by high Galactic extinction, and categorized as extragalactic sources according to our far-infrared- color based criterion (<CitationRef CitationID="CR36">Pollo et al., 2010). This is the first measurement of the large-scale angular clustering of galaxies selected in the far-infrared after IRAS measurements. Although a full description of the clustering properties of these galaxies will be obtained by more detailed studies, using either a spatial correlation function, or better information about properties and, at least, photometric redshifts of these galaxies, the angular correlation function remains the first diagnostic tool to establish the clustering properties of the catalog and the observed galaxy population. We find a non-zero clustering signal in both hemispheres extending up to ~40 degrees, without any significant fluctuations at larger scales. The observed correlation function is well fitted by a power-law function. The notable differences between the northern and southern hemispheres are found, which can probably be attributed to the photometry problems, and might point to the necessity of performing a better calibration in the data from the southern hemisphere.
T. Kondo, H. Kaneda, D. Ishihara, Shinki Oyabu, M. Yamagishi and T. Onaka : Large-scale extraplanar PAH emission in the Galactic center region found by AKARI mid-infrared all-sky survey, Proceedings of The Life Cycle of Dust in the Universe: Observations, 33, 2013.
(要約)
AKARI carried out all-sky surveys at wavelengths of 9, 18, 65, 90, 140 and 160 ? m. Among them, the 9 ? m map can efficiently trace the emission features of polycyclic aromatic hydrocarbons (PAHs). Utilizing this unique all-sky PAH map, we investigate the distribution of the PAH emission for the whole Galactic plane. In particular, the Galactic center regions suffer foreground contamination by the zodiacal light, and therefore we have carefully removed the zodiacal light component by modifying the Kelsall model. As a result, we find that the PAH emission is extended very widely (? 30? ) toward the north direction from the Galactic center region. Since it is known that there are very nearby (?150 pc) Ophiuchus clouds toward similar directions, we subtracted the foreground component associated with these clouds using the HI data. As a result, we confirm that there still remains a significant fraction of the widely-extended PAH emission toward this direction, suggesting that the excess PAH emission originates in the Galactic center region. The spatial distribution resembles that of the Fermi bubbles, well-known gamma-ray structures, which are thought to be created by a past outflow in the Galactic center. Moreover, the PAH/dust ratio is significantly enhanced in the region showing the excess PAH emission. The high PAH/dust ratio is possibly created by shattering of carbonaceous grains in the past outflow from the Galactic center.
D. Ishihara, H. Kaneda, T. Kondo, T. Amatsutsu, K. Nakamichi, M. Yamagishi, Shinki Oyabu, T. Ootsubo and T. Onaka : AKARI mid-infrared all-sky survey: development of the new inter-planetary dust (IPD) map and the world-first all-sky PAH map, Proceedings of The Life Cycle of Dust in the Universe: Observations, 108, 2013.
(要約)
We are constructing accurately calibrated 9 ?m and 18 ?m all-sky diffuse maps from the AKARI mid-infrared all-sky survey data. These maps are heavily affected by the foreground emission of the zodiacal light, which has an intensity peak at around these wavelengths. We carefully separate the zodiacal emission component from the maps using Kelsall's model. Through improvement of the parameters in the zodiacal light emission model, we obtained new insight on the structure and composition of the interplanetary dust in our solar system. The zodiacal light removed AKARI 9 ?m map is the world's first all-sky PAH map, that traces the emission features of Galactic polycyclic aromatic hydrocarbons (PAHs) at wavelengths of 6.2, 7.7, 8.6, and 11.3 ?m. On a global scale, PAHs show good spatial correlation with tracers of general ISM such as CO, HI, and far-IR dust emissions. On a local scale, we recognize the variation of physical state and compositions of hydrocarbons reflecting the variation of the local physical environment. This PAH map will be effectively used in diagnoses of various interstellar phenomena.
76.
Satoshi Takita, Norio Ikeda, Yoshimi Kitamura, Daisuke Ishihara, Hirokazu Kataza, Akiko Kawamura, Shinki Oyabu, Munetaka Ueno and Issei Yamamura : Slow-Scan Observations with the Infrared Camera (IRC) aboard AKARI, Publications of the Astronomical Society of Japan, Vol.64, No.6, 126, 2012.
(要約)
We present the characterization and calibration of the slow-scan observation mode of the Infrared Camera (IRC) aboard AKARI. The IRC Slow-scan observations were operated at the S9W (9μm) and L18W (18μm) bands. We developed a toolkit for data reduction of the IRC Slow-scan observations. We introduced a "self-pointing reconstruction" method to improve the positional accuracy to as good as 1". The sizes of the point spread functions were derived to be ?6" at the S9W band and ?7" at the L18W bands in full width at half maximum. Flux calibrations were achieved with observations of 3 and 4 infrared standard stars at the S9W and L18W bands, respectively. The flux uncertainties are estimated to be better than 20% from comparisons with the AKARI IRC PSC and the WISE preliminary catalog.
(キーワード)
infrared: general / space vehicles / techniques: image processing / Astrophysics - Instrumentation and Methods for Astrophysics
J. S. Kim, M. H. Lee, H. Matsuhara, T. Wada, Shinki Oyabu, M. Im, Y. Jeon, E. Kang, J. Ko, G. M. Lee, T. Takagi, C. Pearson, J. G. White, -S. W. Jeong, S. Serjeant, T. Nakagawa, Y. Ohyama, T. Goto, T. T. Takeuchi, A. Pollo, A. Solarz and A. P?piak : The North Ecliptic Pole Wide survey of AKARI: a near- and mid-infrared source catalog, Astronomy & Astrophysics, Vol.548, A29, 2012.
(要約)
We present a photometric catalog of infrared (IR) sources based on the North Ecliptic Pole Wide field (NEP-Wide) survey of AKARI, which is an infrared space telescope launched by Japan. The NEP-Wide survey covered 5.4 deg2 area, a nearly circular shape centered on the NEP, using nine photometric filter-bands from 2-25 μm of the Infrared Camera (IRC). Extensive efforts were made to reduce possible false objects due to cosmic ray hits, multiplexer bleeding phenomena around bright sources, and other artifacts. The number of detected sources varied depending on the filter band: with about 109 000 sources being cataloged in the near-infrared (NIR) bands at 2-5 μm, about 20 000 sources in the shorter parts of the mid-infrard (MIR) bands between 7-11 μm, and about 16 000 sources in the longer parts of the MIR band, with ~4000 sources at 24 μm. The estimated 5ς detection limits are approximately 21 mag (mag) in the 2-5 μm bands, 19.5-19 mag in the 7-11 μm, and 18.8-18.5 mag in the 15-24 μm bands in the AB magnitude scale. The completenesses for those bands were evaluated as a function of magnitude: the 50% completeness limits are about 19.8 mag at 3 μm, 18.6 mag at 9 μm, and 18 mag at 18 μm band, respectively. To construct a reliable source catalog, all of the detected sources were examined by matching them with those in other wavelength data, including optical and ground-based NIR bands. The final band-merged catalog contains about 114 800 sources detected in the IRC filter bands. The properties of the sources are presented in terms of the distributions in various color-color diagrams. The full version of Table 4 is only available at the CDS via anonymous ftp to cdsarc.u-strasbg.fr (130.79.128.5) or via http://cdsarc.u-strasbg.fr/viz- bin/qcat?J/A+A/548/A29
(キーワード)
methods: data analysis / catalogs / infrared: / galaxies / surveys / Astrophysics - Cosmology and Nongalactic Astrophysics
Y. Matsuoka, N. Ienaka, Shinki Oyabu, K. Wada and S. Takino : Updated Analysis of a "Dark" Galaxy and Its Blue Companion in the Virgo Cloud H I 1225 + 01, The Astronomical Journal, Vol.144, No.6, 159, 2012.
(要約)
H I 1225+01 is an intergalactic gas cloud located on the outskirts of Virgo cluster. Its main components are two large clumps of comparable H I masses (M_{Hathsc{i}} im 109 M_dot) separated by about 100 kpc. One of the clumps hosts a blue low-surface-brightness galaxy J1227+0136, while the other has no identified stellar emission and is sometimes referred to as a promising candidate of a "dark galaxy," an optically invisible massive intergalactic system. We present a deep optical image covering the whole H I 1225+01 structure for the first time, as well as a collection of archival data from ultraviolet to far- infrared (IR) spectral region of the brightest knot "R1" in J1227+0136. We find that R1 has a young stellar population 10-100 Myr in age and mass ~106 M ?, near-IR excess brightness which may point to the presence of hot dust with color temperature ~600 K, and relatively faint mid- to far-IR fluxes corresponding to the dust mass of up to ~100 M ?. Overall, it seems to share the general properties with low-metallicity blue compact dwarf galaxies. On the other hand, no optical counterpart to the other clump is found in our deepest-ever image. Now the limiting surface brightness reaches down to R AB > 28 mag arcsec-2 for any emission extended over 10'' (comparable to R1), which is more than one hundred times fainter than the brightest part of the companion galaxy J1227+0136.
(キーワード)
galaxies: dwarf / galaxies: individual: J1227+0136 / galaxies: ISM / galaxies: star formation / intergalactic medium / radio lines: galaxies / Astrophysics - Cosmology and Nongalactic Astrophysics / Astrophysics - Astrophysics of Galaxies
Hoon Ji Kim, Myungshin Im, Mok Hyung Lee, Gyoon Myung Lee, David Hyunsung Jun, Takao Nakagawa, Hideo Matsuhara, Takehiko Wada, Shinki Oyabu, Toshinobu Takagi, Hanae Inami, Youichi Ohyama, Rika Yamada, George Helou, Lee Armus and Yong Shi : The 3.3 μm Polycyclic Aromatic Hydrocarbon Emission as a Star Formation Rate Indicator, The Astrophysical Journal, Vol.760, No.2, 120, 2012.
(要約)
Polycyclic aromatic hydrocarbon (PAH) emission features dominate the mid-infrared spectra of star-forming galaxies and can be useful to calibrate star formation rates (SFRs) and diagnose ionized states of grains. However, the PAH 3.3 μm feature has not been studied as much as other PAH features since it is weaker than others and resides outside of Spitzer capability. In order to detect and calibrate the 3.3 μm PAH emission and investigate its potential as an SFR indicator, we carried out an AKARI mission program, AKARI mJy Unbiased Survey of Extragalactic Sources (AMUSES), and compared its sample with various literature samples. We obtained 2-5 μm low-resolution spectra of 20 flux-limited galaxies with mixed spectral energy distribution classes, which yielded the detection of the 3.3 μm PAH emission from 3 out of 20 galaxies. For the combined sample of AMUSES and literature samples, the 3.3 μm PAH luminosities correlate with the infrared luminosities of star-forming galaxies, albeit with a large scatter (1.5 dex). The correlation appears to break down at the domain of ultraluminous infrared galaxies (ULIRGs), and the power of the 3.3 μm PAH luminosity as a proxy for the infrared luminosity is hampered at log[L PAH3.3 erg-1 s-1] > ~42.0. Possible origins for this deviation in the correlation are discussed, including contributions from active galactic nuclei and strongly obscured young stellar objects, and the destruction of PAH molecules in ULIRGs.
(キーワード)
galaxies: active / galaxies: ISM / galaxies: starburst / galaxies: star formation / infrared: galaxies / Astrophysics - Cosmology and Extragalactic Astrophysics
J. Glenn White, Bunyo Hatsukade, Chris Pearson, Toshinobu Takagi, Chris Sedgwick, Shuji Matsuura, Hideo Matsuhara, Stephen Serjeant, Takao Nakagawa, Mok Hyung Lee, Shinki Oyabu, Woong-Seob Jeong, Mai Shirahata, Kotaro Kohno, Issei Yamamura, Hitoshi Hanami, Tomotsugu Goto, Sin'itirou Makiuti, L. David Clements, K. Malek and A. Sophia Khan : A deep ATCA 20 cm radio survey of the AKARI Deep Field South near the South Ecliptic Pole, Monthly Notices of the Royal Astronomical Society, Vol.427, No.3, 1830-1846, 2012.
(要約)
The results of a deep radio survey at 20 cm wavelength are reported for a region containing the AKARI Deep Field South (ADF-S) near the South Ecliptic Pole (SEP), using the Australia Telescope Compact Array (ATCA). The survey (hereafter referred to as the ATCA-ADFS survey) has 1ς detection limits ranging from 18.7 to 50 μJy beam-1 over an area of ?1.1 deg2, and ?2.5 deg2 to lower sensitivity. The observations, data reduction and source count analysis are presented along with a description of the overall scientific objectives, and a catalogue containing 530 radio sources detected with a resolution of 6.2 × 4.9 arcsec. The derived differential source counts show a pronounced excess of sources fainter than ?1 mJy, consistent with an emerging population of star-forming galaxies. Cross-correlating the radio with AKARI sources and archival data we find 95 cross-matches, with most galaxies having optical R-magnitudes in the range 18-24 mag, similar to that found in other optical deep field identifications, and 52 components lying within 1 arcsec of a radio position in at least one further catalogue (either IR or optical). We have reported redshifts for a sub-sample of our catalogue finding that they vary between galaxies in the local Universe and those having redshifts of up to 0.825. Associating the radio sources with the Spitzer catalogue at 24 μm, we find 173 matches within one Spitzer pixel, of which a small sample of the identifications are clearly radio loud compared to the bulk of the galaxies. The radio luminosity plot and a colour-colour analysis suggest that the majority of the radio sources are in fact luminous star-forming galaxies rather than radio-loud active galactic nuclei (AGN). There are additionally five cross-matches between the Atacama Submillimetre Telescope Experiment (ASTE) or the Balloon-borne Large Aperture Submillimetre Telescope (BLAST) galaxies and radio sources from this survey, two of which are also detected at 90 μm, and 41 cross-matches with submillimetre sources detected in the Herschel Multi-tiered Extragalactic Survey (HerMES) Public Data release.
(キーワード)
surveys / inrared: galaxies / radio continuum: galaxies / submillimetre: galaxies / Astrophysics - Cosmology and Nongalactic Astrophysics
Kazumi Murata, Hideo Matsuhara, Toshinobu Takagi, Takehiko Wada, Shinki Oyabu and Nagisa Oi : Improvement of Akari Nep-Deep 2-24 Micron Images/catalogues with New Calibrations, Publications of The Korean Astronomical Society, Vol.27, No.4, 149-150, 2012.
D. Ishihara, H. Kaneda, A. Mouri, T. Kondo, S. Suzuki, Shinki Oyabu, T. Onaka, Y. Ita, M. Matsuura and N. Matsunaga : Lifecycle of the Interstellar Dust Grains in Our Galaxy Viewed with Akari/mir All-Sky Survey, Publications of The Korean Astronomical Society, Vol.27, No.4, 117-122, 2012.
H. Matsuhara, T. Wada, T. Takagi, T. Nakagawa, K. Murata, S. Churei, T. Goto, Shinki Oyabu, T. T. Takeuchi, Y. Ohyama, T. Miyaji, M. Krumpe, M. H. Lee, M. Im, S. Serjeant, P. C. Peason, G. White, A. M. Malkan, H. Hanami, T. Ishigaki, D. Burgarella and AKARI NEP Team : Overview of the North Ecliptic Pole Deep Multi-Wavelength Survey NEP-DEEP, Publications of The Korean Astronomical Society, Vol.27, No.4, 123-128, 2012.
Y. Kiriyama, D. Ishihara, T. Nagayama, H. Kaneda, Shinki Oyabu, T. Onaka and H. Fujiwara : Debris Disks Explored by Akari and Irsf, Publications of The Korean Astronomical Society, Vol.27, No.4, 181-182, 2012.
S. Takita, H. Kataza, Y. Kitamura, M. Ueno, Shinki Oyabu, D. Ishihara and Y. Ita : a Survey of T Tauri Stars with Akari, Publications of The Korean Astronomical Society, Vol.27, No.4, 185-186, 2012.
A. Mouri, H. Kaneda, D. Ishihara, Shinki Oyabu, T. Kondo, S. Suzuki, A. Yasuda and T. Onaka : A Study of the Galactic Center Regions Using the Improved Data of the Mid-Infrared All-Sky Survey, Publications of The Korean Astronomical Society, Vol.27, No.4, 217-218, 2012.
M. Yamagishi, H. Kaneda, Shinki Oyabu, D. Ishihara, T. Onaka, T. Shimonishi and T. Suzuki : Systematic Study of Interstellar Ices in Nearby Galaxies, Publications of The Korean Astronomical Society, Vol.27, No.4, 249-252, 2012.
T. Kondo, H. Kaneda, Shinki Oyabu, D. Ishihara, T. Mori, M. Yamagishi, T. Onaka, I. Sakon and T. Suzuki : The Central Region of the Barred Spiral Galaxy NGC 1097 Probed by Akari Near-Infrared Spectroscopy, Publications of The Korean Astronomical Society, Vol.27, No.4, 257-258, 2012.
T. Mori, Shinki Oyabu, H. Kaneda, D. Ishihara and M. Yamagishi : Properties of Dust in Early-Type Galaxies Based on the All-Sky Data and Near-Infrared Spectra, Publications of The Korean Astronomical Society, Vol.27, No.4, 263-264, 2012.
Shinki Oyabu, D. Ishihara, R. Yamada, H. Kaneda, M. Yamagishi, Y. Toba, H. Matsuhara, T. Nakagawa, M. Malkan and M. Shirahata : Survey of Dusty Active Galactic Nuclei Based on the Mid-Infrared All-Sky Survey Catalog, Publications of The Korean Astronomical Society, Vol.27, No.4, 265-270, 2012.
Kohei Ichikawa, Yoshihiro Ueda, Yuichi Terashima, Shinki Oyabu, Poshak Gandhi, Keiko Matsuta and Takao Nakagawa : Mid- and Far-Infrared Properties of Local Active Galactic Nuclei, Publications of The Korean Astronomical Society, Vol.27, No.4, 275-279, 2012.
K. Matsuta, P. Gandhi, T. Dotani, T. Nakagawa, N. Isobe, Y. Ueda, K. Ichikawa, Y. Terashima, Shinki Oyabu, I. Yamamura and L. Stawarz : Infrared and Hard X-Ray Diagnostics of AGN Identification from the Akari and Swift/bat All-Sky Surveys, Publications of The Korean Astronomical Society, Vol.27, No.4, 285-286, 2012.
M. Shirahata, T. Usuda, Shinki Oyabu, T. Nakagawa and I. Yamamura : Near-Infrared High-Resolution Spectroscopy of the Obscured AGN IRAS 01250+2832, Publications of The Korean Astronomical Society, Vol.27, No.4, 295-296, 2012.
R. Yamada, Shinki Oyabu, H. Kaneda, M. Yamagishi, D. Ishihara, H. J. Kim, M. Im, Y. Toba and H. Matsuhara : The 3.3 Micron PAH Emission of the Mid-Infrared Excess Galaxies Discovered by the Akari Mid-Infrared All-Sky Survey, Publications of The Korean Astronomical Society, Vol.27, No.4, 299-300, 2012.
T. Takagi, H. Matsuhara, T. Wada, Y. Ohyama and Shinki Oyabu : A Multi-Wavelength Study of Pah-Selected Starburst Galaxies, Publications of The Korean Astronomical Society, Vol.27, No.4, 321-324, 2012.
Yoshiki Toba, Shinki Oyabu, Hideo Matsuhara, Daisuke Ishihara, Matt Malkan, Takehiko Wada, Youichi Ohyama, Hirokazu Kataza and Satoshi Takita : The 18 μm Luminosity Function of Galaxies with Akari, Publications of The Korean Astronomical Society, Vol.27, No.4, 335-338, 2012.
A. Pollo, T. T. Takeuchi, L. T. Suzuki and Shinki Oyabu : Angular Clustering of Fir-Selected Galaxies in the Akari All-Sky Survey, Publications of The Korean Astronomical Society, Vol.27, No.4, 343-344, 2012.
(要約)
We present the first measurement of the angular two-point correlation function for AKARI 90-$u$m point sources, detected outside of the Milky Way plane and other regions characterized by high Galactic extinction, and categorized as extragalactic sources according to our far-infrared-color based criterion (Pollo et al. 2010). This is the first measurement of the large-scale angular clustering of galaxies selected in the far-infrared after IRAS measurements. Although a full description of clustering properties of these galaxies will be obtained by more detailed studies, using either spatial correlation function, or better information about properties and at least photometric redshifts of these galaxies, the angular correlation function remains the first diagnostics to establish the clustering properties of the catalog and observed galaxy population. We find a non-zero clustering signal in both hemispheres extending up to $im 40$ degrees, without any significant fluctuations at larger scales. The observed correlation function is well fitted by a power law function. The notable differences between a northern and southern hemisphere are found, which can be probably attributed to the photometry problems and point out to a necessity of performing a better calibration in the data from southern hemisphere.
(キーワード)
Astrophysics - Cosmology and Extragalactic Astrophysics
Chris Sedgwick, Stephen Serjeant, Chris Pearson, Toshinobu Takagi, Hideo Matsuhara, Takehiko Wada, Mok Hyung Lee, Myungshin Im, Woong-Seob Jeong, Shinki Oyabu and J. Glenn White : Detection of Hα Emission from z>3.5 Galaxies with Akari-Fuhyu NIR Spectroscopy, Publications of The Korean Astronomical Society, Vol.27, No.4, 357-360, 2012.
T. Matsumoto, J. H. Seo, S. W. Jeong, M. H. Lee, S. Matsuura, H. Matsuhara, Shinki Oyabu, J. Pyo and T. Wada : Akari Observation of the Fluctuation of the Near-Infrared Background, Publications of The Korean Astronomical Society, Vol.27, No.4, 363-365, 2012.
Hitoshi Hanami, Tsuyoshi Ishigaki, Naofumi Fujishiro, Kouichiro Nakanishi, Takamitsu Miyaji, Mirko Krumpe, Keiichi Umetsu, Youichi Ohyama, Hyunjin Shim, Myungshin Im, Mok Hyoung Lee, Gyoon Myung Lee, Stephen Serjeant, J. Glenn White, N. Christopher Willmer, Tomotsugu Goto, Shinki Oyabu, Toshinobu Takagi, Takehiko Wada and Hideo Matsuhara : Star Formation and AGN Activity in Galaxies Classified Using the 1.6 μm Bump and PAH Features at z = 0.4-2, Publications of the Astronomical Society of Japan, Vol.64, No.4, 70, 2012.
(要約)
We have studied the star-formation and AGN activity of massive galaxies in the redshift range $z=0.4-2$, which are detected in a deep survey field using the AKARI InfraRed (IR) astronomical satellite and {m Subaru} telescope toward the North Ecliptic Pole (NEP). The AKARI/IRC Mid-InfraRed (MIR) multiband photometry is used to trace their star- forming activities with the Polycyclic-Aromatic Hydrocarbon (PAH) emissions, which is also used to distinguish star-forming populations from AGN dominated ones and to estimate the Star Formation Rate (SFR) derived from their total emitting IR (TIR) luminosities. In combination with analyses of their stellar components, we have studied the MIR SED features of star-forming and AGN-harboring galaxies.
(キーワード)
Astrophysics - Cosmology and Nongalactic Astrophysics
K. Matsuta, P. Gandhi, T. Dotani, T. Nakagawa, N. Isobe, Y. Ueda, K. Ichikawa, Y. Terashima, Shinki Oyabu, I. Yamamura and ?. Stawarz : Infrared and Hard X-Ray Diagnostics of Active Galactic Nucleus Identification from the Swift/BAT and AKARI All-sky Surveys, The Astrophysical Journal, Vol.753, No.2, 104, 2012.
(要約)
We combine data from two all-sky surveys in order to study the connection between the infrared and hard X-ray (>10 keV) properties for local active galactic nuclei (AGNs). The Swift Burst Alert Telescope all-sky survey provides an unbiased, flux-limited selection of hard X -ray-detected AGNs. Cross-correlating the 22 month hard X-ray survey with the AKARI all-sky survey, we studied 158 AGNs detected by the AKARI instruments. We find a strong correlation for most AGNs between the infrared (9, 18, and 90 μm) and hard X-ray (14-195 keV) luminosities, and quantify the correlation for various subsamples of AGNs. Partial correlation analysis confirms the intrinsic correlation after removing the redshift contribution. The correlation for radio galaxies has a slope and normalization identical to that for Seyfert 1 galaxies, implying similar hard X-ray/infrared emission processes in both. In contrast, Compton-thick (CT) sources show a large deficit in the hard X-ray band, because high gas column densities diminish even their hard X-ray luminosities. We propose two photometric diagnostics for source classification: one is an X-ray luminosity versus infrared color diagram, in which type 1 radio-loud AGNs are well isolated from the others in the sample. The other uses the X-ray versus infrared color as a useful redshift-independent indicator for identifying CT AGNs. Importantly, CT AGNs and starburst galaxies in composite systems can also be differentiated in this plane based upon their hard X-ray fluxes and dust temperatures. This diagram may be useful as a new indicator to classify objects in new and upcoming surveys such as WISE and NuSTAR.
(キーワード)
galaxies: active / infrared: galaxies / X-rays: galaxies / Astrophysics - High Energy Astrophysical Phenomena
Kohei Ichikawa, Yoshihiro Ueda, Yuichi Terashima, Shinki Oyabu, Poshak Gandhi, Keiko Matsuta and Takao Nakagawa : Mid- and Far-infrared Properties of a Complete Sample of Local Active Galactic Nuclei, The Astrophysical Journal, Vol.754, No.1, 45, 2012.
(要約)
We investigate the mid- (MIR) to far-infrared (FIR) properties of a nearly complete sample of local active galactic nuclei (AGNs) detected in the Swift/Burst Alert Telescope (BAT) all-sky hard X-ray (14-195 keV) survey, based on the cross correlation with the AKARI infrared survey catalogs complemented by those with Infrared Astronomical Satellite and Wide-field Infrared Survey Explorer. Out of 135 non-blazer AGNs in the Swift/BAT nine-month catalog, we obtain the MIR photometric data for 128 sources either in the 9, 12, 18, 22, and/or 25 μm band. We find good correlation between their hard X-ray and MIR luminosities over three orders of magnitude (42 < log λL λ(9, 18 μm) < 45), which is tighter than that with the FIR luminosities at 90 μm. This suggests that thermal emission from hot dusts irradiated by the AGN emission dominate the MIR fluxes. Both X-ray unabsorbed and absorbed AGNs follow the same correlation, implying isotropic infrared emission, as expected in clumpy dust tori rather than homogeneous ones. We find excess signals around 9 μm in the averaged infrared spectral energy distribution from heavy obscured "new type" AGNs with small scattering fractions in the X-ray spectra. This could be attributed to the polycyclic aromatic hydrocarbon emission feature, suggesting that their host galaxies have strong starburst activities.
(キーワード)
galaxies: active / galaxies: nuclei / infrared: galaxies / Astrophysics - Astrophysics of Galaxies / Astrophysics - Cosmology and Nongalactic Astrophysics
AKARI, the Japanese infrared astronomical satellite launched in February 2006, exhausted its liquid helium cryogen in August 2007. For about one and a half years of the cold mission phase, AKARI performed all-sky surveys in the two mid-infrared photometric bands centered at 9 and 18 microns with higher spatial resolutions and sensitivities than IRAS. Both bands cover slightly shorter wavelength ranges than the IRAS 12 and 25 micron bands and thus provide different information on the infrared sky. In particular, the AKARI 9 micron band map has unique advantage in tracing the distribution of polycyclic aromatic hydrocarbons (PAHs) for the whole sky. To enable discussion on faint diffuse interstellar emission, we have improved the AKARI mid-infrared all-sky diffuse maps by correcting artifacts such as those caused by space ionizing radiation and scattered light from the moon and very bright sources. The quality of these diffuse maps are now being checked within the AKARI team. We plan to release them to the public in near future.
SPICA (Space Infrared Telescope for Cosmology and Astrophysics) is an astronomical mission optimized for mid- and far-infrared astronomy, envisioned for launch in early 2020s. The core wavelength coverage of this mission is 5 to 210 micron. We present two SPICA Instruments in the mid-infrared region, Mid-infrared Camera and Spectrometer (MCS) and SPICA Coronagraphic Instrument (SCI). MCS will provide imaging and spectroscopic observing capabilities in the mid-infrared region with 4 modules. WFC (Wide Field Camera) has two 5 arcminutes square filed of view and covers the wavelength range 5 to 38 micron, HRS (High Resolution Spectrometer) covers the wavelength range 12 to 18 micron with resolving power about 30000, MRS (Mid Resolution Spectrometer) has integral field units by image slicer and covers the wavelength range 12 to 38 micron simultaneously using dichroic filter and two sets of spectrometers with (spectral) resolving power of 1100--3000, LRS (Low Resolution Spectrometer) adopts prism disperser and covers the wavelength range 5 to 48 micron with resolving power 50 to 100. SCI has been designed for a concentrated study of extra-solar planets (exoplanets). The primary objectives for the SCI are the direct coronagraphic detection and spectroscopy of Jovian exoplanets in infrared, while the monitoring of transiting planets is another important target. In the SCI, coronagraphic and non-coronagraphic modes are applicable for both an imaging and a spectroscopy. The core wavelength range of the SCI is 3.5-27 micron. The SCI has capability of simultaneous observations of one target using two channels, a short channel with an InSb detector and a long wavelength channel with a Si:As detector.
105.
A. Solarz, A. Pollo, T. T. Takeuchi, A. Pȩpiak, H. Matsuhara, T. Wada, Shinki Oyabu, T. Takagi, T. Goto, Y. Ohyama, P. C. Pearson, H. Hanami and T. Ishigaki : Star-galaxy separation in the AKARI NEP deep field, Astronomy & Astrophysics, Vol.541, A50, 2012.
(要約)
Context. It is crucial to develop a method for classifying objects detected in deep surveys at infrared wavelengths. We specifically need a method to separate galaxies from stars using only the infrared information to study the properties of galaxies, e.g., to estimate the angular correlation function, without introducing any additional bias. Aims: We aim to separate stars and galaxies in the data from the AKARI north ecliptic pole (NEP) deep survey collected in nine AKARI/IRC bands from 2 to 24 μm that cover the near- and mid-infrared wavelengths (hereafter NIR and MIR). We plan to estimate the correlation function for NIR and MIR galaxies from a sample selected according to our criteria in future research. Methods: We used support vector machines (SVM) to study the distribution of stars and galaxies in the AKARIs multicolor space. We defined the training samples of these objects by calculating their infrared stellarity parameter (sgc). We created the most efficient classifier and then tested it on the whole sample. We confirmed the developed separation with auxiliary optical data obtained by the Subaru telescope and by creating Euclidean normalized number count plots. Results: We obtain a 90% accuracy in pinpointing galaxies and 98% accuracy for stars in infrared multicolor space with the infrared SVM classifier. The source counts and comparison with the optical data (with a consistency of 65% for selecting stars and 96% for galaxies) confirm that our star/galaxy separation methods are reliable. Conclusions: The infrared classifier derived with the SVM method based on infrared sgc - selected training samples proves to be very efficient and accurate in selecting stars and galaxies in deep surveys at infrared wavelengths carried out without any previous target object selection.
(キーワード)
infrared: galaxies / infrared: stars / galaxies: fundamental parameters / galaxies: statistics / Astrophysics - Instrumentation and Methods for Astrophysics / Astrophysics - Cosmology and Nongalactic Astrophysics
Toru Kondo, Hidehiro Kaneda, Shinki Oyabu, Daisuke Ishihara, Tatsuya Mori, Mitsuyoshi Yamagishi, Takashi Onaka, Itsuki Sakon and Toyoaki Suzuki : The Central Region of the Barred Spiral Galaxy NGC 1097 Probed by AKARI Near-infrared Spectroscopy, The Astrophysical Journal, Vol.751, No.1, L18, 2012.
(要約)
With the Infrared Camera on board AKARI, we carried out near-infrared (2.5-5.0 μm) spectroscopy of the central kiloparsec region of the barred spiral galaxy, NGC 1097, categorized as Seyfert 1 with a circumnuclear starburst ring. Our observations mapped the area of ~50'' × 10'' with the resolution of ~5'', covering about a half of the ring and the galactic center. As a result, we spatially resolve the starburst ring in the polycyclic aromatic hydrocarbon 3.3 μm, the aliphatic hydrocarbon 3.4-3.6 μm features, and the hydrogen Brα 4.05 μm emission. They exhibit spatial distributions significantly different from each other, indicating that the environments vary considerably around the ring. In particular, the aliphatic features are enhanced near the bar connecting the ring with the nucleus, where the structure of hydrocarbon grains seems to be relatively disordered. Near the center, the continuum emission and the CO/SiO absorption features are strong, which indicates that the environments inside the ring are dominated by old stellar populations. The near-infrared spectra do not show any evidence for the presence of nuclear activity.
(キーワード)
galaxies: individual: NGC 1097 / galaxies: ISM / galaxies: nuclei / galaxies: starburst / infrared: galaxies / Astrophysics - Astrophysics of Galaxies
Hidehiro Kaneda, Daisuke Ishihara, Akio Mouri, Shinki Oyabu, Mitsuyoshi Yamagishi, Toru Kondo, Takashi Onaka, Yasuo Fukui, Akiko Kawamura and Kazufumi Torii : Processing of Polycyclic Aromatic Hydrocarbons in Molecular-Loop Regions near the Galactic Center Revealed by AKARI, Publications of the Astronomical Society of Japan, Vol.64, No.2, 25, 2012.
(要約)
We present an AKARI mid-infrared diffuse map of an area of about 4° × 3° near the Galactic center in the 9 μm band. The band intensity is mostly attributed to aromatic hydrocarbon infrared emissions of carbonaceous grains at wavelengths of 6.2, 7,7, 8.6, and 11.3 μm. We detected 9 μm emission structures extending from the Galactic plane up to a latitude of ? 2°.5, which have spatial correspondence to molecular loops revealed by NANTEN 12CO (J = 1-0) observations. We have found that the surface brightness at 9 μm is suppressed near the foot points of the CO loops. The ratios of the 9 μm to the IRAS 100 μm brightness show significant depression near such bright regions in CO emission. With AKARI near-infrared 2.5-5 μm spectroscopy, we find that the 3.3 μm aromatic hydrocarbon emission is absent in the region associated with the loop, suggesting the processing and destruction of carbonaceous grains in the CO molecular loops.
(キーワード)
infrared: general / infrared: ISM / ISM: dust / extinction / ISM: lines and bands / ISM: molecules / ISM: structure / Astrophysics - Astrophysics of Galaxies
Jongwan Ko, Myungshin Im, Mok Hyung Lee, Gyoon Myung Lee, Jin Seong Kim, Hyunjin Shim, Yiseul Jeon, Seong Ho Hwang, A. Christopher N. Willmer, A. Matthew Malkan, Casey Papovich, J. Benjamin Weiner, Hideo Matsuhara, Shinki Oyabu and Toshinobu Takagi : AKARI Observation of the North Ecliptic Pole (NEP) Supercluster at z = 0.087: Mid-infrared View of Transition Galaxies, The Astrophysical Journal, Vol.745, No.2, 181, 2012.
(要約)
We present the mid-infrared (MIR) properties of galaxies within a supercluster in the north ecliptic pole region at z ~ 0.087 observed with the AKARI satellite. We use data from the AKARI NEP-Wide (5.4 deg2) IR survey and the CLusters of galaxies EVoLution studies (CLEVL) mission program. We show that near-IR (3 μm)-mid-IR (11 μm) color can be used as an indicator of the specific star formation rate and the presence of intermediate-age stellar populations. From the MIR observations, we find that red-sequence galaxies consist not only of passively evolving red early-type galaxies, but also of (1) "weak-SFGs" (disk-dominated star-forming galaxies that have star formation rates lower by ~4 × than blue-cloud galaxies) and (2) "intermediate-MXGs" (bulge-dominated galaxies showing stronger MIR dust emission than normal red early-type galaxies). These two populations can be a set of transition galaxies from blue, star-forming, late-type galaxies evolving into red, quiescent, early-type ones. We find that the weak-SFGs are predominant at intermediate masses (1010 M ? < M * < 1010.5 M ?) and are typically found in local densities similar to the outskirts of galaxy clusters. As much as 40% of the supercluster member galaxies in this mass range can be classified as weak-SFGs, but their proportion decreases to <10% at larger masses (M * > 1010.5 M ?) at any galaxy density. The fraction of the intermediate-MXG among red- sequence galaxies at 1010 M ? < M * < 1011 M ? also decreases as the density and mass increase. In particular, ~42% of the red-sequence galaxies with early-type morphologies are classified as intermediate-MXGs at intermediate densities. These results suggest that the star formation activity is strongly dependent on the stellar mass, but that the morphological transformation is mainly controlled by the environment.
T. Takagi, H. Matsuhara, T. Goto, H. Hanami, M. Im, K. Imai, T. Ishigaki, M. H. Lee, G. M. Lee, M. Malkan, Y. Ohyama, Shinki Oyabu, P. C. Pearson, S. Serjeant, T. Wada and J. G. White : The AKARI NEP-Deep survey: a mid-infrared source catalogue, Astronomy & Astrophysics, Vol.537, A24, 2012.
(要約)
We present a new catalogue of mid-IR sources using the AKARI NEP-Deep survey. The InfraRed Camera (IRC) onboard AKARI has a comprehensive mid- IR wavelength coverage with 9 photometric bands at 2-24 μm. We utilized all of these bands to cover a nearly circular area adjacent to the north ecliptic pole (NEP). We designed the catalogue to include most of sources detected in 7, 9, 11, 15 and 18 μm bands, and found 7284 sources in a 0.67 deg2 area. From our simulations, we estimate that the catalogue is ~80 per cent complete to 200 μJy at 15-18 μm, and ~10 per cent of sources are missed, owing to source blending. Star-galaxy separation is conducted using only AKARI photometry, as a result of which 10 per cent of catalogued sources are found to be stars. The number counts at 11, 15, 18, and 24 μm are presented for both stars and galaxies. A drastic increase in the source density is found in between 11 and 15 μm at the flux level of ~ 300 μJy. This is likely due to the redshifted PAH emission at 8 μm, given our rough estimate of redshifts from an AKARI colour-colour plot. Along with the mid-IR source catalogue, we present optical-NIR photometry for sources falling inside a Subaru/Sprime-cam image covering part of the AKARI NEP-Deep field, which is deep enough to detect most of AKARI mid-IR sources, and useful to study optical characteristics of a complete mid-IR source sample. Full Tables 4 and 5 are only available at the CDS via anonymous ftp to cdsarc.u-strasbg.fr (130.79.128.5) or via http://cdsarc.u-strasbg.fr/viz- bin/qcat?J/A+A/537/A24
(キーワード)
methods: data analysis / infrared: galaxies / surveys / catalogs / Astrophysics - Cosmology and Extragalactic Astrophysics
T. Matsumoto, J. H. Seo, -S. W. Jeong, M. H. Lee, S. Matsuura, H. Matsuhara, Shinki Oyabu, J. Pyo and T. Wada : AKARI Observation of the Fluctuation of the Near-infrared Background, The Astrophysical Journal, Vol.742, No.2, 124, 2011.
(要約)
We report a search for fluctuations of the sky brightness toward the north ecliptic pole with the Japanese infrared astronomical satellite AKARI, at 2.4, 3.2, and 4.1 μm. We obtained circular maps with 10' diameter fields of view, which clearly show a spatial structure on the scale of a few hundred arcseconds. A power spectrum analysis shows that there is a significant excess fluctuation at angular scales larger than 100'' that cannot be explained by zodiacal light, diffuse Galactic light, shot noise of faint galaxies, or clustering of low-redshift galaxies. These results are consistent with observations at 3.6 and 4.5 μm by NASA's Spitzer Space Telescope. The fluctuating component observed at large angular scales has a blue stellar spectrum which is similar to that of the spectrum of the excess isotropic emission observed with the Infrared Telescope in Space. A significant spatial correlation between wavelength bands was found, and the slopes of the linear correlations are consistent with the spectrum of the excess fluctuation. These findings indicate that the detected fluctuation could be attributed to the first stars of the universe, i.e., Population III stars. The observed fluctuation provides an important constraint on the era of the first stars.
(キーワード)
cosmology: observations / diffuse radiation / early universe / Astrophysics - Cosmology and Nongalactic Astrophysics
Fumihiko Usui, Daisuke Kuroda, G. Thomas M?ller, Sunao Hasegawa, Masateru Ishiguro, Takafumi Ootsubo, Daisuke Ishihara, Hirokazu Kataza, Satoshi Takita, Shinki Oyabu, Munetaka Ueno, Hideo Matsuhara and Takashi Onaka : Asteroid Catalog Using Akari: AKARI/IRC Mid-Infrared Asteroid Survey, Publications of the Astronomical Society of Japan, Vol.63, No.5, 1117-1138, 2011.
(要約)
We present the results of an unbiased asteroid survey in the mid- infrared wavelength region with the Infrared Camera (IRC) on board the Japanese infrared satellite AKARI. About 20% of the point source events recorded in the AKARI All-Sky Survey observations are not used for the IRC Point Source Catalog (IRC-PSC) in its production process because of a lack of multiple detection by position. Asteroids, which are moving objects on the celestial sphere, remain in these ``residual events''. We identify asteroids out of the residual events by matching them with the positions of known asteroids. For the identified asteroids, we calculate the size and albedo based on the Standard Thermal Model. Finally we have a new brand of asteroid catalog, named the Asteroid Catalog Using AKARI (AcuA), which contains 5120 objects, about twice as many as the IRAS asteroid catalog. The catalog objects comprise 4953 main belt asteroids, 58 near-Earth asteroids, and 109 Jovian Trojan asteroids. The catalog is publicly available via the Internet.
(キーワード)
catalogs / infrared: solar system / minor planets / asteroids / space vehicles: instruments / surveys
Chris Sedgwick, Stephen Serjeant, Chris Pearson, Shuji Matsuura, Mai Shirahata, Shinki Oyabu, Tomotsugu Goto, Hideo Matsuhara, L. D. Clements, Mattia Negrello and J. Glenn White : Far-infrared luminosity function of local star-forming galaxies in the AKARI Deep Field-South, Monthly Notices of the Royal Astronomical Society, Vol.416, 1862, 2011.
(要約)
We present a far-infrared galaxy luminosity function for the local universe. We have obtained 389 spectroscopic redshifts for galaxies observed at 90 μm in the AKARI Deep Field-South, using the AAOmega fibre spectrograph via optical identifications in the digitized sky survey and 4-m class optical imaging. For the luminosity function presented in this paper, we have used those galaxies which have redshifts 0 < z < 0.25, have optical magnitudes and are not part of a newly discovered cluster of galaxies (giving a total of 130 sources). Infrared and optical completeness functions were estimated using earlier Spitzer data and automated plate measurement (APM) B-band optical data, respectively, and the luminosity function has been prepared using the 1/Vmax method. We also separate the luminosity function between galaxies which show evidence of predominantly star-forming activity and predominantly active galactic nucleus (AGN) activity in their optical spectra. Our luminosity function is in good agreement with the previous 90-μm luminosity function from the European Large Area Infrared Space Observatory (ISO) Survey, and we also present a luminosity function with combined AKARI and ISO data. The result is in reasonable agreement with predictions based on the earlier Infrared Astronomical Satellite (IRAS) ?m PSCz catalogue, and with a recent backward evolution model.
Y. Matsuoka, N. Ienaka, K. Kawara and Shinki Oyabu : Cosmic Optical Background: The View from Pioneer 10/11, The Astrophysical Journal, Vol.736, No.2, 119, 2011.
(要約)
We present the new constraints on the cosmic optical background (COB) obtained from an analysis of the Pioneer 10/11 Imaging Photopolarimeter (IPP) data. After careful examination of data quality, the usable measurements free from the zodiacal light are integrated into sky maps at the blue (~0.44 μm) and red (~0.64 μm) band. Accurate starlight subtraction is achieved by referring to all-sky star catalogs and a Galactic stellar population synthesis model down to 32.0 mag. We find that the residual light is separated into two components: one component shows a clear correlation with thermal 100 μm brightness, while another betrays a constant level in the lowest 100 μm brightness region. The presence of the second component is significant after all the uncertainties and possible residual light in the Galaxy are taken into account, and thus it most likely has the extragalactic origin (i.e., the COB). The derived COB brightness is (1.8 ± 0.9) × 10-9 and (1.2 ± 0.9) × 10-9 erg s-1 cm-2 sr-1 ?-1 at the blue and red bands, respectively, or 7.9 ± 4.0 and 7.7 ± 5.8 nW m-2 sr-1. From comparison with the integrated brightness of galaxies, we conclude that bulk of the COB is comprised of normal galaxies which have already been resolved in the current deepest observations. There seems to be little room for contributions of other populations including "first stars" at these wavelengths. On the other hand, the first component of the IPP residual light represents the diffuse Galactic light (DGL)?scattered starlight by the interstellar dust. We derive mean DGL-to-100 μm brightness ratios of 2.1 × 10-3 and 4.6 × 10-3 at the two bands, which are roughly consistent with the previous observations toward the denser dust regions. Extended red emission in the diffuse interstellar medium is also confirmed.
(キーワード)
cosmic background radiation / cosmology: observations / dark ages / reionization / first stars / dust / extinction / galaxies: evolution / infrared: ISM / Astrophysics - Cosmology and Nongalactic Astrophysics / Astrophysics - Astrophysics of Galaxies
S. Matsuura, M. Shirahata, M. Kawada, T. T. Takeuchi, D. Burgarella, L. D. Clements, -S. W. Jeong, H. Hanami, A. S. Khan, H. Matsuhara, T. Nakagawa, Shinki Oyabu, P. C. Pearson, A. Pollo, S. Serjeant, T. Takagi and J. G. White : Detection of the Cosmic Far-infrared Background in AKARI Deep Field South, The Astrophysical Journal, Vol.737, No.1, 2, 2011.
(要約)
We report new limits on the absolute brightness and spatial fluctuations of the cosmic infrared background (CIB) via the AKARI satellite. We carried out observations at 65, 90, 140, and 160 μm as a cosmological survey in AKARI Deep Field South, which is one of the lowest cirrus regions with a contiguous area of the sky. After removing bright galaxies and subtracting zodiacal and Galactic foregrounds from the measured sky brightness, we successfully measured the CIB brightness and its fluctuations across a wide range of angular scales, from arcminutes to degrees. The measured CIB brightness is consistent with previous results reported from COBE data, but significantly higher than the lower limits at 70 and 160 μm obtained via Spitzer from the stacking analysis of selected 24 μm sources. The discrepancy with the Spitzer result is possibly due to a new galaxy population at high redshift obscured by hot dust or unknown diffuse emission. From a power spectrum analysis at 90 μm, two components were identified: the CIB fluctuations with shot noise due to individual galaxies in a small angular scale from the beam size up to 10 arcminutes, and Galactic cirrus emission dominating at the largest angular scales of a few degrees. The overall shape of the power spectrum at 90 μm is very similar to that at longer wavelengths, as observed by Spitzer and the Balloon-borne Large-Aperture Submillimeter Telescope (BLAST). Our power spectrum, with an intermediate angular scale of 10-30 arcminutes, gives a firm upper limit for galaxy clustering, which was found by Spitzer and BLAST. Moreover, the color of the CIB fluctuations, which is obtained by combining our data with the previous results, is as red as ultra-luminous infrared galaxies at high redshift. These galaxies are not likely to provide the majority of the CIB emission at 90 μm, but are responsible for the fluctuations. Our results provide new constraints on the evolution and clustering properties of distant infrared galaxies and any diffuse emission from the early universe.
(キーワード)
cosmology: observations / diffuse radiation / infrared: diffuse background / infrared: galaxies / large-scale structure of universe / Astrophysics - Cosmology and Nongalactic Astrophysics / Astrophysics - Astrophysics of Galaxies
Tatsuya Mori, Hidehiro Kaneda, Daisuke Ishihara, Shinki Oyabu and Takehiko Wada : Laboratory and In-Flight Measurements at 10-55 K of InSb Near-Infrared Detector Performance for the Warm Mission of the AKARI Satellite, Publications of the Astronomical Society of the Pacific, Vol.123, No.906, 942, 2011.
(要約)
The warm mission phase of AKARI, the Japanese infrared astronomical satellite, has started after its 180 liter liquid helium cryogen was exhausted. Since then, we have conducted near-infrared observations with the Infrared Camera (IRC), while the telescope is slowly warming up. To explore the possibility of continuing observations at higher temperatures, we evaluate the performance of the InSb detector array, a flight backup model for the IRC, in a laboratory at various operating temperatures between 10 K and 55 K. By combining the laboratory measurements with the in-flight measurements of the AKARI/IRC detector array, we consistently derive the changes of relative sensitivity, dark current, total noise, and the number of hot pixels with operating temperature. All of them show small changes in a range of temperature from 10 K to 40 K. However, at temperatures above 40 K, the dark current and the number of hot pixels start to increase rapidly, while the relative sensitivity decreases and the total noise increases gradually. We obtain the dependence of the performance on bias voltages to suggest an optimal operation for a future AKARI warmer phase.
Ko Arimatsu, Takashi Onaka, Itsuki Sakon, Shinki Oyabu, Yoshifusa Ita, Toshihiko Tanab?, Daisuke Kato, Fumi Egusa, Takehiko Wada and Hideo Matsuhara : Characterization and Improvement of the Image Quality of the Data Taken with the Infrared Camera (IRC) Mid-Infrared Channels on Board AKARI, Publications of the Astronomical Society of the Pacific, Vol.123, No.906, 981, 2011.
(要約)
Mid-infrared images frequently suffer artifacts and extended point- spread functions (PSFs). We investigate the characteristics of the artifacts and the PSFs in images obtained with the infrared camera (IRC) on board AKARI at four mid-infrared bands of the S7 (7 μm), S11 (11 μm), L15 (15 μm), and L24 (24 μm). Removal of the artifacts significantly improves the reliability of the reference data for flat-fielding at the L15 and L24 bands. A set of models of the IRC PSFs is also constructed from on-orbit data. These PSFs have extended components that come from diffraction and scattering within the detector arrays. We estimate the aperture correction factors for point sources and the surface brightness correction factors for diffuse sources. We conclude that the surface brightness correction factors range from 0.95 to 0.8, taking account of the extended component of the PSFs. To correct for the extended PSF effects for the study of faint structures, we also develop an image reconstruction method, which consists of the deconvolution with the PSF and the convolution with an appropriate Gaussian. The appropriate removal of the artifacts, improved flat-fielding, and image reconstruction with the extended PSFs enable us to investigate detailed structures of extended sources in IRC mid-infrared images.
(キーワード)
Astrophysics - Instrumentation and Methods for Astrophysics
Tomotsugu Goto, Stephane Arnouts, Matthew Malkan, Toshinobu Takagi, Hanae Inami, Chris Pearson, Takehiko Wada, Hideo Matsuhara, Chisato Yamauchi, T. Tsutomu Takeuchi, Takao Nakagawa, Shinki Oyabu, Daisuke Ishihara, B. David Sanders, Emeric Floc'h Le, Mok Hyung Lee, Woong-Seob Jeong, Stephen Serjeant and Chris Sedgwick : Infrared luminosity functions of AKARI Sloan Digital Sky Survey galaxies, Monthly Notices of the Royal Astronomical Society, Vol.414, No.3, 1903-1913, 2011.
(要約)
By cross-correlating the AKARI all-sky survey in six infrared (IR) bands (9, 18, 65, 90, 140 and 160 μm) with the Sloan Digital Sky Survey (SDSS) galaxies, we identified 2357 IR galaxies with a spectroscopic redshift. This is not just one of the largest samples of local IR galaxies, but AKARI provides crucial far-IR (FIR) bands for accurately measuring the galaxy spectral energy distribution (SED) across the peak of the dust emission at > 100 μ m. By fitting modern IR SED models to the AKARI photometry, we measured the total infrared luminosity (LIR) of individual galaxies. Using this LIR, we constructed the luminosity functions (LF) of IR galaxies at a median redshift of z= 0.031. The LF agrees well with that at z= 0.0082 (the Revised Bright Galaxy Sample), showing smooth and continuous evolution towards higher redshift LFs measured in the AKARI North Ecliptic Pole (NEP) deep field. By integrating the IR LF weighted by LIR, we measured the local cosmic IR luminosity density of ΩIR= (3.8+5.8-1.2) × 108 L? Mpc-3. We separate galaxies into active galactic nuclei (AGN), star-forming galaxies (SFG) and composite by using the [N II]/Hα versus [O III]/Hβ line ratios. The fraction of AGN shows a continuous increase with increasing LIR from 25 to 90 per cent at 9 < log LIR < 12.5. The SFRHα and ? show good correlations with LIR for SFG and AGN, respectively. The self-absorption-corrected Hα/Hβ ratio shows a weak increase with LIR with a substantial scatter. When we separate IR LFs into contributions from AGN and SFG, the AGN contribution becomes dominant at LIR > 1011 L?, coinciding with the break of both the SFG and AGN IR LFs. At LIR? 1011 L?, SFG dominates IR LFs. Only 1.1 ± 0.1 per cent of ΩIR is produced by luminous infrared galaxies (LIR > 1011 L?), and only 0.03 ± 0.01 per cent by ultraluminous infrared galaxies (LIR > 1012 L?) in the local Universe. Compared with high-redshift results from the AKARI NEP deep survey, we observed a strong evolution of ΩSFGIR∝ (1 +z)4.1±0.4 and ΩAGNIR∝ (1 +z)4.1±0.5. Our results show that all of our measured quantities (IR LFs, L*, ΩAGNIR, ΩSFGIR) show smooth and steady increase from lower redshift (the Revised Bright Galaxy Sample) to higher redshift (the AKARI NEP deep survey).
C. Yamauchi, S. Fujishima, N. Ikeda, K. Inada, M. Katano, H. Kataza, S. Makiuti, K. Matsuzaki, S. Takita, Y. Yamamoto, I. Yamamura, D. Ishihara and Shinki Oyabu : AKARI-CAS Online Service for AKARI All-Sky Catalogues, Publications of the Astronomical Society of the Pacific, Vol.123, No.905, 852, 2011.
(要約)
The AKARI All-Sky Catalogues are an important infrared astronomical database for next-generation astronomy that take over the IRAS catalog. We have developed an online service, AKARI Catalogue Archive Server (AKARI-CAS), for astronomers. The service includes useful and attractive search tools and visual tools. One of the new features of AKARI-CAS is cached SIMBAD/NED entries, which can match AKARI catalogs with other catalogs stored in SIMBAD or NED. To allow advanced queries to the databases, direct input of SQL is also supported. In those queries, fast dynamic cross-identification between registered catalogs is a remarkable feature. In addition, multiwavelength quick-look images are displayed in the visualization tools, which will increase the value of the service. In the construction of our service, we considered a wide variety of astronomers' requirements. As a result of our discussion, we concluded that supporting users' SQL submissions is the best solution for the requirements. Therefore, we implemented an RDBMS layer so that it covered important facilities, including the whole processing of tables. We found that PostgreSQL is the best open-source RDBMS products for such purpose, and we wrote codes for both simple and advanced searches into the SQL stored functions. To implement such stored functions for fast radial search and cross-identification with minimum cost, we applied a simple technique that is not based on HTM or HEALPix. In contrast, the online application layer became compact and was written in simple procedural PHP codes. In total, our system realizes cost-effective maintenance and enhancements.
(キーワード)
Astrophysics - Instrumentation and Methods for Astrophysics
Hidehiro Kaneda, Takehiko Wada, Shinki Oyabu, Ryoko Kano, Yuichi Kiriyama, Yasuki Hattori, Toyoaki Suzuki, Kensuke Ide, Masahiro Kato and Kentaroh Watanabe : Electrical and Photoconductive Properties at 1.8 K of Germanium p+-i Junction Device Fabricated by Surface-Activated Wafer Bonding, Japanese Journal of Applied Physics, Vol.50, No.6R, 066503, 2011.
(要約)
We have evaluated the electrical and photoconductive properties of a Ge p+-i junction device, fabricated by surface-activated wafer bonding (SAB) technology, at temperatures of 1.8-5 K. The p+-i junction consists of two bonded layers, Ge heavily doped with Ga at a concentration of 1×1016 cm-3 and non- doped intrinsic Ge. The bonded Ge wafer was diced to a 1-mm cubic test element having two layers of thickness 0.5 mm and two facing electrodes. We measured the current-voltage characteristics of the device at 1.8-5 K, and its photoresponses against stepped illumination with far-infrared light at 1.8 K. The device shows the expected cryogenic performance in terms of electrical and photoconductive properties, demonstrating the promising applicability of SAB-processed Ge p+-i junction devices in blocked-impurity-band-type Ge detectors.
Hidehiro Kaneda, Daisuke Ishihara, Takashi Onaka, Toyoaki Suzuki, Tatsuya Mori, Shinki Oyabu and Mitsuyoshi Yamagishi : Properties of Dust and PAHs in the Hot Plasma of the Elliptical Galaxy NGC 4125 Revealed with AKARI and Spitzer Space Telescope, Publications of the Astronomical Society of Japan, Vol.63, No.3, 601-615, 2011.
(要約)
We present the spatial distributions of dust and polycyclic aromatic hydrocarbons (PAHs) in the elliptical galaxy NGC 4125, revealed by AKARI and Spitzer. NGC 4125 is relatively bright in dust and PAH emision for elliptical galaxies, although it certainly possesses diffuse interstellar hot plasma, indicated by the high spatial resolution X-ray data of Chandra. We investigate how the dust and PAHs interact with the X-ray plasma or avoid the interaction by comparing their spatial distributions. We find that the distributions of the PAHs and dust are different from each other, both showing a significant deviation from a smooth stellar distribution. The PAH emission predominantly comes from a dust lane, a compact dense molecular gas region in the galactic center, where the PAHs are likely to have been protected from the interaction with the X-ray plasma. The dust emission has more extended structures, similar to the distribution of the X-ray plasma, suggesting their interaction to some extent. We also discuss a possible origin of the dust and PAHs in the galaxy.
(キーワード)
dust / extinction / galaxies: elliptical and lenticular / cD / galaxies: individual (NGC 4125) / galaxies: ISM / infrared: galaxies / Astrophysics - Cosmology and Nongalactic Astrophysics
Shinki Oyabu, D. Ishihara, M. Malkan, H. Matsuhara, T. Wada, T. Nakagawa, Y. Ohyama, Y. Toba, T. Onaka, S. Takita, H. Kataza, I. Yamamura and M. Shirahata : AKARI detections of hot dust in luminous infrared galaxies. Search for dusty active galactic nuclei, Astronomy & Astrophysics, Vol.529, A122, 2011.
(要約)
Aims: We present a new sample of active galactic nuclei (AGNs) identified using the catalog of the AKARI Mid-infrared (MIR) All-Sky Survey. Our MIR search has the advantage of detecting AGNs that are obscured at optical wavelengths by extinction. Methods: We first selected AKARI 9 μm excess sources with F(9 μm)/F(KS) > 2 where KS magnitudes were taken from the Two Micron All Sky Survey. We then obtained follow-up near-infrared spectroscopy with the AKARI/IRC to confirm that the excess is caused by hot dust. We also obtained optical spectroscopy with the Kast Double Spectrograph on the Shane 3-m telescope at Lick Observatory. Results: On the basis of these observations, we detected hot dust with a characteristic temperature of ? 500 K in two luminous infrared galaxies. The hot dust is suspected to be associated with AGNs that exhibit their nonstellar activity not in the optical, but in the near- and mid-infrared bands, i.e., they harbor buried AGNs. The host galaxy stellar masses of ~4-6 × 109 M? are small compared with the hosts in optically-selected AGN populations. These objects were missed by previous surveys, demonstrating the power of the AKARI MIR All-Sky Survey to widen AGN searches to include more heavily obscured objects. The existence of multiple dusty star clusters with massive stars cannot be completely ruled out with our current data.
(キーワード)
galaxies: active / galaxies: nuclei / infrared: galaxies
A. Mouri, H. Kaneda, D. Ishihara, Shinki Oyabu, M. Yamagishi, T. Mori, T. Onaka, T. Wada and H. Kataza : Effects of High-Energy Ionizing Particles on the Si:As Mid-Infrared Detector Array on Board the AKARI Satellite, Publications of the Astronomical Society of the Pacific, Vol.123, No.903, 561-567, 2011.
(要約)
We evaluate the effects of high-energy ionizing particles on the Si:As impurity band conduction (IBC) mid-infrared detector on board AKARI, the Japanese infrared astronomical satellite. IBC-type detectors are known to be little influenced by ionizing radiation. However, we find that the detector is significantly affected by in-orbit ionizing radiation even after spikes induced by ionizing particles are removed. The effects are described as changes mostly in the offset of detector output, but not in the gain. We conclude that the changes in the offset are caused mainly by increase in dark current. We establish a method to correct these ionizing radiation effects. The method is essential to improve the quality and to increase the sky coverage of the AKARI mid-infrared all- sky-survey map.
(キーワード)
Astrophysics - Instrumentation and Methods for Astrophysics
Mitsuyoshi Yamagishi, Hidehiro Kaneda, Daisuke Ishihara, Shinki Oyabu, Takashi Onaka, Takashi Shimonishi and Toyoaki Suzuki : AKARI Near-infrared Spectroscopic Observations of Interstellar Ices in the Edge-on Starburst Galaxy NGC 253, The Astrophysical Journal, Vol.731, No.1 PART II, L20, 2011.
(要約)
We present the spatially resolved near-infrared (2.5-5.0 μm) spectra of the edge-on starburst galaxy NGC 253 obtained with the Infrared Camera on board AKARI. Near the center of the galaxy, we clearly detect the absorption features of interstellar ices (H2O: 3.05 μm, CO2: 4.27 μm, and XCN: 4.62 μm) and the emission of polycyclic aromatic hydrocarbons (PAHs) at 3.29 μm and the hydrogen recombination line Brα at 4.05 μm. We find that the distributions of the ices differ from those of the PAH and gas. We calculate the column densities of the ices and derive the abundance ratios of N(CO2)/N(H2O) = 0.17 ± 0.05. They are similar to those obtained around the massive young stellar objects in our Galaxy (0.17 ± 0.03), although a much stronger interstellar radiation field and higher dust temperature are expected near the center of NGC 253.
(キーワード)
galaxies: individual: NGC 253 / galaxies: ISM / infrared: galaxies / ISM: abundances / ISM: molecules / Astrophysics - Astrophysics of Galaxies
K. Kawara, H. Hirashita, T. Nozawa, T. Kozasa, Shinki Oyabu, Y. Matsuoka, T. Shimizu, H. Sameshima and N. Ienaka : Supernova dust for the extinction law in a young infrared galaxy at z? 1, Monthly Notices of the Royal Astronomical Society, Vol.412, No.2, 1070-1080, 2011.
(要約)
We apply the supernova (SN) extinction curves to reproduce the observed properties of SST J1604+4304 which is a young infrared (IR) galaxy at z? 1. The SN extinction curves used in this work were obtained from models of unmixed ejecta of Type II supernovae for the Salpeter initial mass function with a mass range from 8 to 30 M? or 8 to 40 M?. The effect of dust distributions on the attenuation of starlight is investigated by performing the χ2 fitting method against various dust distributions. These are the commonly used uniform dust screen, the clumpy dust screen and the internal dust geometry. We add to these geometries three scattering properties, namely, no scattering, isotropic scattering and forward-only scattering. Judging from the χ2 values, we find that the uniform screen models with any scattering property provide good approximations to the real dust geometry. Internal dust is inefficient to attenuate starlight and thus cannot be the dominant source of the extinction. We show that the SN extinction curves reproduce the data of SST J1604+4304 comparable to or better than the Calzetti extinction curve. The Milky Way extinction curve is not in satisfactory agreement with the data unless several dusty clumps are in the line of sight. This trend may be explained by the abundance of SN-origin dust in these galaxies; SN dust is the most abundant in the young IR galaxy at z? 1, abundant in local starbursts and less abundant in the Galaxy. If dust in SST J1604+4304 is dominated by SN dust, the dust production rate is ?0.1 M? per SN.
(キーワード)
supernovae: general / dust / extinction / galaxies: evolution / galaxies: ISM / galaxies: starburst / infrared: galaxies / Astrophysics - Cosmology and Nongalactic Astrophysics
K. Kawara, Shinki Oyabu, Y. Matsuoka, Y. Yoshii, T. Minezaki, H. Sameshima, N. Asami, N. Ienaka and T. Kozasa : Erratum: Stellar population and dust extinction in an ultraluminous infrared galaxy at z= 1.135, Monthly Notices of the Royal Astronomical Society, Vol.412, No.3, 2112, 2011.
Kentaro Aoki, Shinki Oyabu, P. Jay Dunn, Nahum Arav, Doug Edmonds, T. Kirk Korista, Hideo Matsuhara and Yoshiki Toba : Outflow in Overlooked Luminous Quasar: Subaru Observations of AKARI J1757+5907, Publications of the Astronomical Society of Japan, Vol.63, No.sp2, S457-S467, 2011.
(要約)
We present Subaru observations of the newly discovered luminous quasar AKARI J1757+5907, which shows an absorption outflow in its spectrum. The absorption consists of 9 distinct troughs, and our analysis focuses on the troughs at ?-1000 km s-1 for which we could measure accurate column densities of He I*, Fe II, and Mg II. We used photoionization models to constrain the ionization parameter, total hydrogen column density, and number density of the outflowing gas. These constraints yielded lower limits for the distance, mass-flow rate, and kinetic luminosity for outflows of 3.7 kpc, 70 Modot yr-1, and 2.0 ×1043 erg s-1, respectively. Such a mass-flow rate value can contribute significantly to metal enrichment of the intra-cluster medium. We found that this moderate velocity outflow is similar to those recently discovered in massive post-starburst galaxies. Finally, we describe the scientific potential of future observations targeting this object.
Tomotsugu Goto, Stephane Arnouts, Hanae Inami, Hideo Matsuhara, Chris Pearson, T. Tsutomu Takeuchi, Emeric Floc'h Le, Toshinobu Takagi, Takehiko Wada, Takao Nakagawa, Shinki Oyabu, Daisuke Ishihara, Hyung Lee Mok, Woong-Seob Jeong, Chisato Yamauchi, Stephen Serjeant, Chris Sedgwick and Ezequiel Treister : Luminosity functions of local infrared galaxies with AKARI: implications for the cosmic star formation history and AGN evolution, Monthly Notices of the Royal Astronomical Society, Vol.410, No.1, 573-584, 2011.
(要約)
Infrared (IR) luminosity is fundamental to understanding the cosmic star formation history and active galactic nuclei (AGN) evolution, since their most intense stages are often obscured by dust. However, local IR luminosity function estimates today are still based on the IRAS survey in the 1980s, with wavelength coverage only up to 100 μm. The AKARI IR space telescope performed an all-sky survey in six IR bands (9, 18, 65, 90, 140 and 160 μm) with 3-10 times better sensitivity, covering the crucial far-IR wavelengths across the peak of the dust emission. Combined with a better spatial resolution, AKARI can much more precisely measure the total infrared luminosity (LTIR) of individual galaxies, and thus, the total infrared luminosity density in the local Universe. By fitting modern IR spectral energy distribution (SED) models, we have remeasured LTIR of the IRAS Revised Bright Galaxy Sample, which is a complete sample of local galaxies with S60 μm > 5.24 Jy. We present mid-IR monochromatic luminosity (νLν) to LTIR correlations for Spitzer8 μm, AKARI9 μm, IRAS12 μm, WISE12 μm, ISO15 μm, AKARI18 μm, WISE22 μm and Spitzer24 μm filters. These measures of LMIR are well correlated with LTIR, with scatter in the range 13-44 per cent. The best-fitting LMIR-to-LTIR conversions provide us with estimates of LTIR using only a single MIR band, in which several deep all-sky surveys are becoming available such as AKARI MIR and WISE. Although we have found some overestimates of LTIR by IRAS due to contaminating cirrus/sources, the resulting AKARI IR luminosity function (LF) agrees well with that from IRAS. We integrate the LF weighted by LTIR to obtain a cosmic IR luminosity density of ΩTIR= (8.5+1.5-2.3) × 107 L? Mpc-3, of which 7 ± 1 per cent is produced by luminous infrared galaxies (LIRGs) (LTIR > 1011 L?), and only 0.4 ± 0.1 per cent is from ultraluminous infrared galaxies (ULIRGs) (LTIR > 1012 L?) in the local Universe, in stark contrast to high-redshift results. We separate the contributions from AGN and star-forming galaxies (SFGs). The SFG IR LF shows a steep decline at the bright end. Combined with high-redshift results from the AKARI NEP deep survey, these data show a strong evolution of ΩSFTIR∝ (1 +z)4.0±0.5 and ΩAGNTIR∝ (1 +z)4.4±0.4. For ΩAGNTIR, the ULIRG contribution exceeds that from LIRGs already by z? 1. A rapid evolution in both ΩAGNTIR and ΩSFGTIR suggests the correlation between star formation and black hole accretion rate continues up to higher redshifts. We compare the evolution of ΩAGNTIR to that of X-ray luminosity density. The ΩAGNTIR/ΩX-rayAGN ratio shows a possible increase at z > 1, suggesting an increase of obscured AGN at z > 1.
H. Sameshima, K. Kawara, Y. Matsuoka, Shinki Oyabu, N. Asami and N. Ienaka : Implications from the optical to ultraviolet flux ratio of Fe II emission in quasars, Monthly Notices of the Royal Astronomical Society, Vol.410, No.2, 1018-1026, 2011.
(要約)
We investigate Fe II emission in the broad-line region (BLR) of active galactic nuclei by analysing the Fe II(UV), Fe II(λ4570) and Mg II emission lines in 884 quasars in the Sloan Digital Sky Survey Quasar catalogue in a redshift range of 0.727 < z < 0.804. Fe II(λ4570)/Fe II(UV) is used to infer the column density of Fe II- emitting clouds and explore the excitation mechanism of Fe II emission lines. As suggested before in various works, the classical photoionization models fail to account for Fe II(λ4570)/Fe II(UV) by a factor of 10, which may suggest anisotropy of UV Fe II emission, or an alternative mechanism like shocks. The column density distribution derived from Fe II(λ4570)/Fe II(UV) indicates that radiation pressure plays an important role in BLR gas dynamics. We find a positive correlation between Fe II(λ4570)/Fe II(UV) and the Eddington ratio. We also find that the ionizing photon fraction must be much smaller than that previously suggested unless Fe II-emitting clouds are super- Eddington. Finally, we propose a physical interpretation of a striking set of correlations between various emission-line properties, known as `Eigenvector 1'.
(キーワード)
atomic processes / line: formation / radiation mechanisms: general / galaxies: active / galaxies: nuclei / quasars: emission lines / Astrophysics - Astrophysics of Galaxies
S. Takita, H. Kataza, Y. Kitamura, D. Ishihara, Y. Ita, Shinki Oyabu and M. Ueno : A survey of T Tauri stars with AKARI towards the Taurus-Auriga region, Astronomy & Astrophysics, Vol.519, A83, 2010.
(要約)
Context. The first Japanese infrared astronomical satellite, AKARI, has completed an All-Sky Survey at mid- to far-infrared wavelengths with higher spatial resolutions and sensitivities than the previous survey with Infrared Astronomical Satellite (IRAS). Aims: We search for new T Tauri star (TTS) candidates with the mid-infrared (MIR) part of the AKARI All-Sky Survey at 9 and 18 μm wavelengths. Methods: We used the point source catalogue (PSC) obtained by the Infrared Camera (IRC) on board AKARI. We combined the 2MASS PSC and the 3rd version of the USNO CCD Astrograph Catalogue (UCAC) with the AKARI IRC-PSC, and surveyed 517 known TTSs over a 1800-square-degree part of the Taurus- Auriga region to develop criteria to extract TTSs. We considered asymptotic giant branch (AGB) stars, post-AGB stars, planetary nebulae (PNe), and galaxies, which have similar MIR colours, to separate TTSs from these sources. We finally searched for new TTS candidates from AKARI IRC-PSC in the same Taurus-Auriga region. Results: Of the 517 known TTSs, we detected 133 sources with AKARI: 46 sources were not detected by IRAS. Based on the colour-colour and colour-magnitude diagrams made from the AKARI, 2MASS, and UCAC surveys, we propose the criteria to extract TTS candidates from the AKARI All-Sky data, and 68/133 AKARI detected TTSs have passed these criteria. On the basis of our criteria, we selected 176/14725 AKARI sources as TTS candidates that are located around the Taurus-Auriga region. Comparing these sources with SIMBAD, we found that 148 are previously identified sources including 115 young stellar objects (YSOs), and 28 unidentified sources. Conclusions: Based on SIMBAD identifications, we infer the TTS- identification probability using our criteria to be ~75%. We find 28 TTS candidates, of which we expect ~21 to be confirmed once follow-up observations can be obtained. Although the probability of ~75% is not so high, it is affected by the completeness of the SIMBAD database, and we can search for TTSs over the whole sky, and all star-forming regions. Tables 1 and 2 are only available in electronic form at the CDS via anonymous ftp to cdsarc.u-strasbg.fr (130.79.128.5) or via http://cdsarc.u-strasbg.fr/viz- bin/qcat?J/A+A/519/A83
(キーワード)
stars: formation / stars: late-type / stars: pre-main sequence / infrared: stars / Astrophysics - Solar and Stellar Astrophysics
J. G. White, C. Pearson, R. Braun, S. Serjeant, H. Matsuhara, T. Takagi, T. Nakagawa, R. Shipman, P. Barthel, N. Hwang, M. H. Lee, G. M. Lee, M. Im, T. Wada, Shinki Oyabu, S. Pak, -Y. M. Chun, H. Hanami, T. Goto and S. Oliver : A deep survey of the AKARI north ecliptic pole field . I. WSRT 20 cm radio survey description, observations and data reduction, Astronomy & Astrophysics, Vol.517, A54, 2010.
(要約)
Aims: The Westerbork Radio Synthesis Telescope, WSRT, has been used to make a deep radio survey of an ~1.7 degree2 field coinciding with the AKARI north ecliptic pole deep field. The observations, data reduction and source count analysis are presented, along with a description of the overall scientific objectives. Methods: The survey consisted of 10 pointings, mosaiced with enough overlap to maintain a similar sensitivity across the central region that reached as low as 21 μJy beam-1 at 1.4 GHz. Results: A catalogue containing 462 sources detected with a resolution of 17.0'' × 15.5'' is presented. The differential source counts calculated from the WSRT data have been compared with those from the shallow VLA-NEP survey of Kollgaard et al. 1994, and show a pronounced excess for sources fainter than ~1 mJy, consistent with the presence of a population of star forming galaxies at sub-mJy flux levels. Conclusions: The AKARI north ecliptic pole deep field is the focus of a major observing campaign conducted across the entire spectral region. The combination of these data sets, along with the deep nature of the radio observations will allow unique studies of a large range of topics including the redshift evolution of the luminosity function of radio sources, the clustering environment of radio galaxies, the nature of obscured radio-loud active galactic nuclei, and the radio /far-infrared correlation for distant galaxies. This catalogue provides the basic data set for a future series of paper dealing with source identifications, morphologies, and the associated properties of the identified radio sources.
(キーワード)
galaxies: active / radio continuum: galaxies / surveys / catalogs / cosmology: observations / Astrophysics - Cosmology and Nongalactic Astrophysics
Takafumi Ootsubo, Fumihiko Usui, Hideyo Kawakita, Masateru Ishiguro, Reiko Furusho, Sunao Hasegawa, Munetaka Ueno, Jun-ichi Watanabe, Tomohiko Sekiguchi, Takehiko Wada, Youichi Ohyama, Shinki Oyabu, Hideo Matsuhara, Takashi Onaka, Takao Nakagawa and Hiroshi Murakami : Detection of Parent H2O and CO2 Molecules in the 2.5-5 μm Spectrum of Comet C/2007 N3 (Lulin) Observed with AKARI, The Astrophysical Journal, Vol.717, No.1, L66, 2010.
(要約)
Comet C/2007 N3 (Lulin) was observed with the Japanese infrared satellite AKARI in the near-infrared at a post-perihelion heliocentric distance of 1.7 AU. Observations were performed with the spectroscopic (2.5-5.0 μm) and imaging (2.4, 3.2, and 4.1 μm) modes on 2009 March 30 and 31 UT, respectively. AKARI images of the comet exhibit a sunward crescent-like shape coma and a dust tail extended toward the anti-solar direction. The 4.1 μm image (CO/CO2 and dust grains) shows a distribution different from the 2.4 and 3.2 μm images (H2O and dust grains). The observed spectrum shows distinct bands at 2.66 and 4.26 μm, attributed to H2O and CO2, respectively. This is the fifth comet in which CO2 has been directly detected in the near-infrared spectrum. In addition, CO at 4.67 μm and a broad 3.2-3.6 μm emission band from C-H bearing molecules were detected in the AKARI spectrum. The relative abundance ratios CO2/H2O and CO/H2O derived from the molecular production rates are ~4%-5% and <2%, respectively. Comet Lulin belongs to the group that has relatively low abundances of CO and CO2 among all observed comets.
Shinki Oyabu, I. Yamamura, C. Alfageme, P. Barthel, A. Cassatella, M. Cohen, N. Cox, E. Figueredo, H. Fujiwara, N. Ikeda, D. Ishihara, -S. W. Jeong, H. Kataza, Do Kester, M. H. Lee, S. Makiuti, G. T. Mueller, T. Nakagawa, S. Takita, H. S. Oh, S. Oliver, C. Pearson, N. Rahman, M. Rowan-Robinson, A. Salama, R. Savage, S. Serjeant, J. G. White and C. Yamauchi : AKARI infrared bright source catalogues, Space Telescopes and Instrumentation 2010: Optical, Infrared, and Millimeter Wave, Vol.7731, 77312P, 2010.
(要約)
Bright source catalogues based on the new mid- and far-infrared all-sky survey by the infrared astronomical satellite AKARI were released into the public domain in March 2010. The mid-infrared catalogue contains more than 870 thousand sources observed at 9 and 18 μm, and the far- infrared catalogue provides information of about 427 thousand sources at 65, 90, 140, and 160 μm. The AKARI catalogues will take over the IRAS catalogues and will become one of the most important catalogues in astronomy. We present the characteristics of the AKARI infrared source catalogues as well as current activity for the future versions.
D. Ishihara, T. Onaka, H. Kataza, A. Salama, C. Alfageme, A. Cassatella, N. Cox, P. García-Lario, C. Stephenson, M. Cohen, N. Fujishiro, H. Fujiwara, S. Hasegawa, Y. Ita, W. Kim, H. Matsuhara, H. Murakami, T. G. Müller, T. Nakagawa, Y. Ohyama, Shinki Oyabu, J. Pyo, I. Sakon, H. Shibai, S. Takita, T. Tanab?, K. Uemizu, M. Ueno, F. Usui, T. Wada, H. Watarai, I. Yamamura and C. Yamauchi : The AKARI/IRC mid-infrared all-sky survey, Astronomy & Astrophysics, Vol.514, A1, 2010.
(要約)
Context. AKARI is the first Japanese astronomical satellite dedicated to infrared astronomy. One of the main purposes of AKARI is the all-sky survey performed with six infrared bands between 9 μm and 200 μm during the period from 2006 May 6 to 2007 August 28. In this paper, we present the mid-infrared part (9 μm and 18 μm bands) of the survey carried out with one of the on-board instruments, the infrared camera (IRC). Aims: We present unprecedented observational results of the 9 μm and 18 μm AKARI all-sky survey and detail the operation and data processing leading to the point source detection and measurements. Methods: The raw data are processed to produce small images for every scan, and the point sources candidates are derived above the 5ς noise level per single scan. The celestial coordinates and fluxes of the events are determined statistically and the reliability of their detections is secured through multiple detections of the same source within milli- seconds, hours, and months from each other. Results: The sky coverage is more than 90% for both bands. A total of 877 091 sources (851 189 for 9 μm, 195 893 for 18 μm) are confirmed and included in the current release of the point source catalog. The detection limit for point sources is 50 mJy and 90 mJy for the 9 μm and 18 μm bands, respectively. The position accuracy is estimated to be better than 2''. Uncertainties in the in-flight absolute flux calibration are estimated to be 3% for the 9 μm band and 4% for the 18 μm band. The coordinates and fluxes of detected sources in this survey are also compared with those of the IRAS survey and are found to be statistically consistent. Catalog is only available in electronic form at the CDS via anonymous ftp to cdsarc.u-strasbg.fr (130.79.128.5) or via http://cdsweb.u-strasbg.fr/cgi- bin/qcat?J/A+A/514/A1
(キーワード)
infrared: general / techniques: image processing / surveys / Astrophysics - Instrumentation and Methods for Astrophysics
Y. Ita, M. Matsuura, D. Ishihara, Shinki Oyabu, S. Takita, H. Kataza, I. Yamamura, N. Matsunaga, T. Tanab?, Y. Nakada, H. Fujiwara, T. Wada, T. Onaka and H. Matsuhara : AKARI's infrared view on nearby stars. Using AKARI infrared camera all-sky survey, 2MASS, and Hipparcos catalogs, Astronomy & Astrophysics, Vol.514, A2, 2010.
(要約)
Context. The AKARI, a Japanese infrared space mission, has performed an All-Sky Survey in six infrared-bands from 9 to 180 μm with higher spatial resolutions and better sensitivities than IRAS. Aims: We investigate the mid-infrared (9 and 18 μm) point source catalog (PSC) obtained with the infrared camera (IRC) onboard AKARI, in order to understand the infrared nature of the known objects and to identify previously unknown objects. Methods: Color-color diagrams and a color-magnitude diagram were plotted with the AKARI-IRC PSC and other available all-sky survey catalogs. We combined the Hipparcos astrometric catalog and the 2MASS all-sky survey catalog with the AKARI-IRC PSC. We furthermore searched literature and SIMBAD astronomical database for object types, spectral types, and luminosity classes. We identified the locations of representative stars and objects on the color-magnitude and color-color diagram schemes. The properties of unclassified sources can be inferred from their locations on these diagrams. Results: We found that the (B-V) vs. (V-S9W) color-color diagram is useful for identifying the stars with infrared excess emerged from circumstellar envelopes or disks. Be stars with infrared excess are separated well from other types of stars in this diagram. Whereas (J-L18W) vs. (S9W- L18W) diagram is a powerful tool for classifying several object types. Carbon-rich asymptotic giant branch (AGB) stars and OH/IR stars form distinct sequences in this color-color diagram. Young stellar objects (YSOs), pre-main sequence (PMS) stars, post-AGB stars, and planetary nebulae (PNe) have the largest mid-infrared color excess and can be identified in the infrared catalog. Finally, we plot the L18W vs. (S9W- L18W) color-magnitude diagram, using the AKARI data together with Hipparcos parallaxes. This diagram can be used to identify low-mass YSOs and AGB stars. We found that this diagram is comparable to the [24] vs. ([8.0]-[24]) diagram of Large Magellanic Cloud sources using the Spitzer Space Telescope data. Our understanding of Galactic objects will be used to interpret color-magnitude diagram of stellar populations in the nearby galaxies that Spitzer Space Telescope observed. Conclusions: Our study of the AKARI color-color and color-magnitude diagrams will be used to explore properties of unknown objects in the future. In addition, our analysis highlights a future key project to understand stellar evolution with a circumstellar envelope, once the forthcoming astronometrical data with GAIA are available. Catalog (full Tables 3 and 4) are only available in electronic form at the CDS via anonymous ftp to cdsarc.u-strasbg.fr (130.79.128.5) or via http://cdsweb.u-strasbg.fr/cgi- bin/qcat?J/A+A/514/A2
(キーワード)
stars: AGB and post-AGB / stars: emission-line / Be / supergiants / stars: Wolf-Rayet / stars: pre-main sequence / infrared: stars / Astrophysics - Solar and Stellar Astrophysics
T. Takagi, Y. Ohyama, T. Goto, H. Matsuhara, Shinki Oyabu, T. Wada, P. C. Pearson, M. H. Lee, M. Im, G. M. Lee, H. Shim, H. Hanami, T. Ishigaki, K. Imai, J. G. White, S. Serjeant and M. Malkan : Polycyclic aromatic hydrocarbon (PAH) luminous galaxies at z ~ 1, Astronomy & Astrophysics, Vol.514, A5, 2010.
(要約)
Aims: The NEP-deep survey, an extragalactic AKARI survey towards the north ecliptic pole (NEP), provides a comprehensive wavelength coverage from 2 to 24 μm using all 9 photometric bands of the infrared camera (IRC). It allows us to photometrically identify galaxies whose mid-IR emission is clearly dominated by PAHs. Methods: We propose a single-colour selection method to identify such galaxies, using two mid-IR flux ratios at 11-to-7 μm and 15-to-9 μm (PAH-to-continuum flux ratio in the rest frame), which are useful for identifying starburst galaxies at z ~ 0.5 and 1, respectively. We perform a fitting of the spectral energy distributions (SEDs) from optical to mid-IR wavelengths, using an evolutionary starburst model with a proper treatment of radiative transfer (SBURT), in order to investigate their nature. Results: The SBURT model reproduces observed optical-to-mid-IR SEDs of more than a half of the PAH-selected galaxies. Based on the 8 μm luminosity, we find ultra luminous infrared galaxies (ULIRGs) among PAH- selected galaxies. Their PAH luminosity is higher than local ULIRGs with a similar luminosity, and the PAH-to-total IR luminosity ratio is consistent with that of less luminous starburst galaxies. They are a unique galaxy population at high redshifts, and we call these PAH- selected ULIRGs ``PAH-luminous'' galaxies. Although they are not as massive as submillimetre galaxies at z ~ 2, they have the stellar mass of > 3 × 1010 M_? and therefore are moderately massive.
(キーワード)
galaxies: starburst / infrared: galaxies / galaxies: active / galaxies : evolution / Astrophysics - Cosmology and Nongalactic Astrophysics / Astrophysics - Astrophysics of Galaxies
T. Goto, T. Takagi, H. Matsuhara, T. T. Takeuchi, C. Pearson, T. Wada, T. Nakagawa, O. Ilbert, E. Floc'h Le, Shinki Oyabu, Y. Ohyama, M. Malkan, M. H. Lee, G. M. Lee, H. Inami, N. Hwang, H. Hanami, M. Im, K. Imai, T. Ishigaki, S. Serjeant and H. Shim : Evolution of infrared luminosity functions of galaxies in the AKARI NEP-deep field. Revealing the cosmic star formation history hidden by dust, Astronomy & Astrophysics, Vol.514, A6, 2010.
(要約)
Aims: Dust-obscured star-formation increases with increasing intensity and increasing redshift. We aim to reveal the cosmic star- formation history obscured by dust using deep infrared observation with AKARI. Methods: We constructed restframe 8 μm, 12 μm, and total infrared (TIR) luminosity functions (LFs) at 0.15 < z < 2.2 using 4128 infrared sources in the AKARI NEP-deep field. A continuous filter coverage in the mid-IR wavelength (2.4, 3.2, 4.1, 7, 9, 11, 15, 18, and 24 μm) by the AKARI satellite allowed us to estimate restframe 8 μm and 12 μm luminosities without using a large extrapolation based on an SED fit, which was the largest uncertainty in previous work. Results: We find that all 8 μm (0.38 < z < 2.2), 12 μm (0.15 < z < 1.16), and TIR LFs (0.2 < z <1.6) show continuous and strong evolution toward higher redshift. Our direct estimate of 8 μm LFs is useful since previous work often had to use a large extrapolation from the Spitzer 24 μm to 8 μm, where SED modeling is more difficult because of the PAH emissions. In terms of cosmic infrared luminosity density (Ω_IR), which was obtained by integrating analytic fits to the LFs, we find good agreement with previous work at z<1.2. We find the Ω_IR evolves as propto(1 + z)4.4± 1.0. When we separate contributions to Ω_IR by LIRGs and ULIRGs, we found more IR luminous sources are increasingly more important at higher redshift. We find that the ULIRG (LIRG) contribution increases by a factor of 10 (1.8) from z = 0.35 to z = 1.4. This research is based on the observations with AKARI, a JAXA project with the participation of ESA.Based on data collected at Subaru Telescope, which is operated by the National Astronomical Observatory of Japan.
(キーワード)
infrared: galaxies / galaxies: luminosity function / mass function / galaxies: evolution / galaxies: high-redshift / galaxies: formation / galaxies: starburst / Astrophysics - Cosmology and Nongalactic Astrophysics
T. Goto, Y. Koyama, T. Wada, C. Pearson, H. Matsuhara, T. Takagi, H. Shim, M. Im, G. M. Lee, H. Inami, M. Malkan, S. Okamura, T. T. Takeuchi, S. Serjeant, T. Kodama, T. Nakagawa, Shinki Oyabu, Y. Ohyama, M. H. Lee, N. Hwang, H. Hanami, K. Imai and T. Ishigaki : Environmental dependence of 8 μm luminosity functions of galaxies at z ~ 0.8. Comparison between RXJ1716.4+6708 and the AKARI NEP-deep field, Astronomy & Astrophysics, Vol.514, A7, 2010.
(要約)
Aims: We aim to reveal environmental dependence of infrared luminosity functions (IR LFs) of galaxies at z ~ 0.8 using the AKARI satellite. AKARI's wide field of view and unique mid-IR filters help us to construct restframe 8 μm LFs directly without relying on SED models. Methods: We construct restframe 8 μm IR LFs in the cluster region RXJ1716.4+6708 at z = 0.81, and compare them with a blank field using the AKARI north ecliptic pole deep field data at the same redshift. AKARI's wide field of view (10' × 10') is suitable to investigate wide range of galaxy environments. AKARI's 15 μm filter is advantageous here since it directly probes restframe 8 μm at z ~ 0.8, without relying on a large extrapolation based on a SED fit, which was the largest uncertainty in previous work. Results: We have found that cluster IR LFs at restframe 8 μm have a factor of 2.4 smaller L^* and a steeper faint-end slope than that of the field. Confirming this trend, we also found that faint-end slopes of the cluster LFs becomes flatter and flatter with decreasing local galaxy density. These changes in LFs cannot be explained by a simple infall of field galaxy population into a cluster. Physics that can preferentially suppress IR luminous galaxies in high density regions is required to explain the observed results. This research is based on the observations with AKARI, a JAXA project with the participation of ESA.Based on data collected at Subaru Telescope, which is operated by the National Astronomical Observatory of Japan.
P. C. Pearson, Shinki Oyabu, T. Wada, H. Matsuhara, M. H. Lee, J. S. Kim, T. Takagi, T. Goto, S. M. Im, S. Serjeant, G. M. Lee, W. J. Ko, J. G. White and O. Ohyama : Source counts at 15 microns from the AKARI NEP survey, Astronomy & Astrophysics, Vol.514, A8, 2010.
(要約)
We present galaxy counts at 15 microns using the Japanese AKARI satelitte's NEP-deep and NEP-wide legacy surveys at the north ecliptic pole. The total number of sources detected are approximately 6700 and 10 700 down to limiting fluxes of 117 and 250 microJy (5 sigma) for the NEP-deep and NEP-wide survey respectively. We construct the Euclidean normalized differential source counts for both data sets (assuming 80 percent completeness levels of 200 and 270 microJy respectively) to produce the widest and deepest contiguous survey at 15 microns to date covering the entire flux range from the deepest to shallowest surveys made with the infrared space observatory (ISO) over areas sufficiently significant to overcome cosmic variance, detecting six times as many sources as the largest survey carried out with ISO. We compare the results from AKARI with the previous surveys with ISO at the same wavelength and the Spitzer observations at 16 microns using the peek-up camera on its IRS instrument. The AKARI source counts are consistent with other results to date reproducing the steep evolutionary rise at fluxes less than a milliJansky and super-Euclidean slopes. We find the the AKARI source counts show a slight excess at fluxes fainter than 200 microJanskys which is not predicted by previous source count models at 15 microns. However, we caution that at this level we may be suffering from the effects of source confusion in our data. At brighter fluxes greater than a milliJansky, the NEP-wide survey source counts agree with the Northern ISO-ELAIS field results, resolving the discrepancy of the bright end calibration in the ISO 15 micron source counts.
P. C. Pearson, S. Serjeant, M. Negrello, T. Takagi, -S. W. Jeong, H. Matsuhara, T. Wada, Shinki Oyabu, M. H. Lee and S. M. Im : The AKARI FU-HYU galaxy evolution program: first results from the GOODS-N field, Astronomy & Astrophysics, Vol.514, A9, 2010.
(要約)
The AKARI FU-HYU mission program carried out mid-infrared imaging of several well studied Spitzer fields preferentially selecting fields already rich in multi-wavelength data from radio to X-ray wavelengths filling in the wavelength desert between the Spitzer IRAC and MIPS bands. We present the initial results for the FU-HYU survey in the GOODS-N field. We utilize the supreme multiwavelength coverage in the GOODS-N field to produce a multiwavelength catalogue from infrared to ultraviolet wavelengths, containing more than 4393 sources, including photometric redshifts. Using the FU-HYU catalogue we present colour- colour diagrams that map the passage of PAH features through our observation bands. We find that the longer mid-infrared bands from AKARI (IRC-L18W 18 micron band) and Spitzer (MIPS24 24 micron band) provide an accurate measure of the total MIR emission of the sources and therefore their probable total mid-infrared luminosity. We also find that colours incorporating the AKARI IRC-S11 11 micron band produce a bimodal distribution where an excess at 11 microns preferentially selects moderate redshift star-forming galaxies. These powerful colour-colour diagnostics are further used as tools to extract anomalous colour populations, in particular a population of Silicate Break galaxies from the GOODS-N field showing that dusty starbursts can be selected of specific redshift ranges (z = 1.2-1.6) by mid-infrared drop-out techniques. The FU-HYU catalogue will be made publically available to the astronomical community.
S. Serjeant, M. Negrello, C. Pearson, A. Mortier, J. Austermann, I. Aretxaga, D. Clements, S. Chapman, S. Dye, J. Dunlop, L. Dunne, D. Farrah, D. Hughes, -M. H. Lee, H. Matsuhara, E. Ibar, M. Im, -S. W. Jeong, S. Kim, Shinki Oyabu, T. Takagi, T. Wada, G. Wilson, M. Vaccari and M. Yun : The AGN fraction of submm-selected galaxies and contributions to the submm/mm-wave extragalactic background light, Astronomy & Astrophysics, Vol.514, A10, 2010.
(要約)
We present a comparison of the SCUBA half degree extragalactic survey (SHADES) at 450 μm, 850 μm and 1100 μm with deep guaranteed time 15 μm AKARI FU-HYU survey data and Spitzer guaranteed time data at 3.6-24 μm in the Lockman hole east. The AKARI data was analysed using bespoke software based in part on the drizzling and minimum-variance matched filtering developed for SHADES, and was cross-calibrated against ISO fluxes. Our stacking analyses find AKARI 15 μm galaxies with ?200 μJy contribute >10% of the 450 μm background, but only <4% of the 1100 μm background, suggesting that different populations contribute at mm- wavelengths. We confirm our earlier result that the ultra-deep 450 μm SCUBA-2 cosmology survey will be dominated by populations already detected by AKARI and Spitzer mid-infrared surveys. The superb mid- infrared wavelength coverage afforded by combining Spitzer and AKARI photometry is an excellent diagnostic of AGN contributions, and we find that (23-52)% of submm-selected galaxies have AGN bolometric fractions fAGN > 0.3.
(キーワード)
galaxies: starburst / infrared: galaxies / galaxies: active / galaxies: statistics / Astrophysics - Cosmology and Nongalactic Astrophysics / Astrophysics - Astrophysics of Galaxies
K. Kawara, Shinki Oyabu, Y. Matsuoka, Y. Yoshii, T. Minezaki, H. Sameshima, N. Asami, N. Ienaka and T. Kozasa : Stellar population and dust extinction in an ultraluminous infrared galaxy at z = 1.135, Monthly Notices of the Royal Astronomical Society, Vol.402, No.1, 335, 2010.
(要約)
We present the detailed optical to far-infrared (far-IR) observations of SST J1604+4304, an ultraluminous IR galaxy at z = 1.135. Analysing the stellar absorption lines, namely, the CaII H & K and Balmer H lines in the optical spectrum, we derive the upper limits of an age for the stellar population. Given this constraint, the minimum χ2 method is used to fit the stellar population models to the observed spectral energy distribution from 0.44 to 5.8 μm. We find the following properties. The stellar population has an age 40-200 Myr with a metallicity 2.5 Zsolar. The starlight is reddened by E(B - V) = 0.8. The reddening is caused by the foreground dust screen, indicating that dust is depleted in the starburst site and the starburst site is surrounded by a dust shell. The IR (8-1000 μm) luminosity is Lir = 1.78 +/- 0.63 × 1012Lsolar. This is two times greater than that expected from the observed starlight, suggesting either that 1/2 of the starburst site is completely obscured at UV-optical wavelengths, or that 1/2 of Lir comes from active galactic nucleus (AGN) emission. The inferred dust mass is 2.0 +/- 1.0 × 108Msolar. This is sufficient to form a shell surrounding the galaxy with an optical depth E(B - V) = 0.8. From our best stellar population model - an instantaneous starburst with an age 40 Myr - we infer the rate of 19 supernovae per year. Simply analytical models imply that 2.5 Zsolar in stars was reached when the gas mass reduced to 30 per cent of the galaxy mass. The gas metallcity is 4.8Zsolar at this point. The gas-to-dust mass ratio is then 120 +/- 73. The inferred dust production rate is 0.24 +/- 0.12Msolar per SN. If 1/2 of Lir comes from AGN emission, the rate is 0.48 +/- 0.24Msolar per SN. We discuss the evolutionary link of SST J1604+4304 to other galaxy populations in terms of the stellar masses and the galactic winds, including optically selected low-luminosity Lyman α-emitters and submillimeter selected high-luminosity galaxies.
D. Ishihara, T. Onaka, H. Kataza, H. Fujiwara, S. Takita, C. Alfageme, M. Cohen, N. Fujishiro, García-Lario P., S. Hasegawa, Y. Ita, W. Kim, T. Nakagawa, H. Matsuhara, T. Matsumoto, H. Murakami, Y. Ohyama, Shinki Oyabu, J. Pyo, I. Sakon, A. Salama, C. Stephenson, H. Shibai, T. Tanabe, K. Uemizu, M. Ueno, F. Usui, T. Wada, H. Watarai, C. Yamauchi and I. Yamamura : AKARI; Mid-Infrared All-Sky Survey, AKARI, a Light to Illuminate the Misty Universe, Vol.418, 9, 2009.
(要約)
AKARI is the first Japanese astronomical infrared satellite mission orbiting around the Earth in a sun-synchronous polar orbit at the altitude of 700 km. One of the major observation programs of the AKARI is an all-sky survey in the mid- to far-infrared spectral regions with 6 photometric bands. The mid-infrared part of the AKARI All-Sky Survey was carried out with the Infrared Camera (IRC) at the 9 and 18 μm bands with the sensitivity of about 50 and 120 mJy (5ς per scan), respectively. The spatial resolution is about 9.4'' at both bands. AKARI mid-infrared (MIR) all-sky survey substantially improves the MIR dataset of the IRAS survey of two decades ago and provides a significant database for studies of various fields of astronomy ranging from star-formation and debris disk systems to cosmology. This paper describes the current status of the data reduction and the characteristics of the AKARI MIR all-sky survey data.
143.
I. Sakon, T. Onaka, T. Wada, F. Usui, H. Kaneda, Y. Ohyama, Shinki Oyabu, D. Ishihara, T. Tanabé, H. Matsuhara, T. Nakagawa, H. Murakami, T. Minezaki, Y. Yoshii, T. Nozawa, K. Nomoto, M. Tanaka, N. Tominaga and T. Kozasa : Near to Mid-Infrared Observations of Recent Supernovae with Infrared Camera (IRC) onboard AKARI, AKARI, a Light to Illuminate the Misty Universe, Vol.418, 181, 2009.
(要約)
We present our latest results on near- to mid-infrared observations of supernovae within one year after the explosion with Infrared Camera (IRC) on board AKARI. In this project, we aim to explore the dust formation scenario in the ejecta of core-collapse supernovae. So far, observations of several recent supernovae including SN2006jc and SN2008ax have been carried out as part of the Directors Time of AKARI. At the same time, we have set about the near-infrared slit-less spectroscopic observations of nearby galaxies with high supernovae frequency in preparation for a future supernova in the AKARI Phase-3 Open Time Program ``Near-infrared Slit-less Spectroscopy of Nearby Galaxies; Waiting for Supernovae Momentarily (NEWSY)'' (P.I. Sakon, I.). The obtained near- to mid-infrared spectral energy distribution (SED) of early-time supernovae is quite valuable and unique to investigate the properties of dust formed around the massive star and will further deepen our knowledge on the origin of dust especially in the early universe.
144.
T. Takagi, H. Matsuhara, T. Wada, Shinki Oyabu, Y. Ohyama, T. Goto, H. Hanami, M. H. Lee, M. Im, S. Serjeant, J. G. White, P. C. Pearson, M. Malkan, D. Burgarella, T. Ishigaki, K. Wada, K. Imai and T. Nakagawa : AKARI Deep Extragalactic Survey towards the North Ecliptic Pole: The NEP-Deep Survey, AKARI, a Light to Illuminate the Misty Universe, Vol.418, 275, 2009.
(要約)
We have conducted the largest extragalactic survey with IRC pointed observations, towards the north ecliptic pole (NEP). Using this survey, which covers 0.38 deg2, we demonstrate that IRC all-band photometry at 2-24 μm is capable of tracing the steep rise of flux at the blue side of PAH 6.2 μm feature. Single mid-infrared colors, such as S11-S7 and L15-S9W, can be used to select PAH-dominated starburst galaxies at z ? 0.5. These PAH-selected galaxies include new type of ultra luminous infrared galaxies whose SED resembles that of less luminous starburst galaxies by two orders of magnitude. We present highlights from the initial results of the NEP-Deep survey.
145.
M. Shirahata, S. Matsuura, M. Kawada, T. T. Takeuchi, T. Takagi, Shinki Oyabu, T. Nakagawa, A. Pollo, P. C. Pearson, S. Serjeant, J. G. White and Akari Mp-Fbsep Team : Far-Infrared Cosmological Survey in AKARI Deep Field South: Galaxy Number Counts, AKARI, a Light to Illuminate the Misty Universe, Vol.418, 301, 2009.
(要約)
The AKARI far-infrared deep cosmological survey has been carried out toward the region with the lowest cirrus density in the whole sky, near the South Ecliptic Pole (AKARI Deep Survey South: ADF-S). We present the details of this survey, and show the obtained galaxy number counts. More than 2200 galaxies were detected down to a flux level of 10 mJy at 90 μm, and suggest the necessity for a new model to explain galaxy evolution.
146.
J. G. White, M. Etxaluze, H. Matsuhara, S. Matsuura, T. Wada, E. Figueredo, M. H. Lee, S. Serjeant, C. Pearson, T. Takagi, I. Yamamura, T. Nakagawa, T. Goto, H. Shibai, C. Sedgwick, M. Negrello, -S. W. Jeong, Shinki Oyabu, M. Shirahata, B. Hatsukade, R. Braun, S. Khan, Akari Fis Team and Iosg Uk-Netherlands Consortium : Tuning in the Radio: Deep Radio Surveys Supporting the AKARI North and South Ecliptic Pole Ultra Deep Fields, AKARI, a Light to Illuminate the Misty Universe, Vol.418, 313, 2009.
(要約)
We present a progress report on two deep radio surveys to support the AKARI North and South Ecliptic Pole Deep fields, and a first correlation between the extragalactic radio source population and their 20 cm fluxes.
147.
C. Pearson, S. Serjeant, T. Takagi, -S. W. Jeong, M. Negrello, H. Matsuhara, T. Wada, Shinki Oyabu, M. H. Lee and M. Im : First Results from the AKARI FU-HYU Mission Program, AKARI, a Light to Illuminate the Misty Universe, Vol.418, 319, 2009.
(要約)
The AKARI FU-HYU mission program has carried out mid-infrared imaging of several well studied Spitzer fields. This imaging fills in the wavelength coverage lacking from the Spitzer surveys and gives an extremely high scientific return for minimal input for AKARI. We select fields already rich in multi-wavelength data from radio to X-ray wavelengths and present the results from our initial analysis in the GOODS-N field. We utilize the comprehansive multiwavelength coverage in the GOODS-N field to produce a multiwavelength catalogue from infrared to ultraviolet wavelengths including photometric redshifts. Using the FU-HYU catalogue we present colour-colour diagrams that map the passage of PAH features through our observation bands. These colour-colours diagrams are used as tools to extract anomalous colour populations, in particular a population of Silicate Break galaxies from the GOODS-N field.
148.
J. S. Kim, M. H. Lee, T. Wada, Shinki Oyabu, Y. Ita, M. Im and H. Matsuhara : NEP-Wide Data Reduction, AKARI, a Light to Illuminate the Misty Universe, Vol.418, 507, 2009.
(要約)
We have carried out a reduction of the ``NEP-Wide'' data for four 9 bands between 2 and 24 μm with the AKARI InfraRed Camera. The data consists of 446 pointed observations and covers a circular area of ? 5.8 sq. deg. centered on North Ecliptic Pole. We made mosaic images in all of the bands except at 24 μm. The source detection and photometry were done on the mosaic images using SExtractor, and we have generated a band merged catalogue for all of the IRC bands (except for 24 μm) containing ?110,000 sources. The photometry was checked against the NEP-Deep results and found to be consistent with them.
149.
T. Takagi, H. Matsuhara, T. Wada, Shinki Oyabu, T. Goto, Y. Ohyama, H. Hanami, P. C. Pearson, S. Serjeant, M. Negrello, G. White, M. Im, M. H. Lee, M. Malkan and Akari Extragalactic Team : A Milestone to SPICA Extragalactic Surveys: The AKARI NEP Survey, The Next-Generation Infrared Space Mission: SPICA, 04017, 2009.
(要約)
Large area surveys in the infrared wavelengths have revealed a significant evolution of the star formation activity of the universe in the past. The extragalactic sur- vey we have conduced with AKARI towards the north ecliptic pole (NEP) is unique, in terms of a comprehensive wavelength coverage from 2 to 24 micron using all 9 photometric bands of the Infrared Camera (IRC). We demonstrate that this IRC all-band photometry is capable of tracing a steep rise in the flux at the blue side of the polycyclic aromatic hydrocarbon (PAH) 6.2 micron emission feature of infrared luminous galaxies at z < 1. This allows us to estimate redshifts of mid-IR sources and identify `ultra-luminous starburst galaxies', based on mid-IR spectral energy distributions (SEDs). SPICA could inherit this unique capability of AKARI and extend the study to typical galaxy populations at z ~ 2, i.e. a critical period of galaxy formation.
Shinki Oyabu, K. Kawara, Y. Tsuzuki, Y. Matsuoka, H. Sameshima, N. Asami and Y. Ohyama : AKARI Near- and Mid-Infrared Spectroscopy of APM 08279+5255 at z = 3.91, The Astrophysical Journal, Vol.697, No.1, 452, 2009.
(要約)
We present rest-frame optical/near-infrared spectra of the gravitationally lensed quasar APM 08279+5255 at z = 3.91 that has been taken using the Infrared Camera (IRC) onboard the AKARI infrared satellite. The observed continuum consists of two components; a power- law component dominating optical wavelengths which is the direct light from the central source and thermal emission dominating near-infrared wavelengths which is attributed to the emission from hot dust in the circumnuclear region. The thermal emission well represents optically thick emission by hot dust at T ~ 1300 K with τ2 μm > 2 and apparent mass, M hot > 10 M sun. Thus, our observations directly detected the optically thick region of hot dust in APM 08279+5255. H I recombination lines of Hα (0.656 μm), Paα (1.875 μm), and Paβ (1.282 μm) are clearly detected at 3.2, 6.3, and 9.3 μm. Simulations with the photoionization models suggest that APM 08279+5255 has broad-line region (BLR) clouds characterized by log n H ~ 12-14 for the gas density, log U ~ -2 to -6 for the ionization parameter, and E(B - V) ~ 0.3-0.6 for the BLR. Thus, optically thick emission of hot dust supports an idea on nonspherical distribution of dust near the central source, consistent with the active galactic nuclei model with the dust torus. The temperature of hot dust and flux ratios of these H I lines are similar to those observed in low-redshift quasars. There are significant time variations in the H I lines, which are probably caused by variations in the brightness of the central source. Based on observations with AKARI, a JAXA project with the participation of ESA.
(キーワード)
galaxies: active / infrared: galaxies / quasars: emission lines / quasars: general / quasars: individual: APM 08279+5255 / Astrophysics - Cosmology and Extragalactic Astrophysics
H. Sameshima, J. Maza, Y. Matsuoka, Shinki Oyabu, K. Kawara, Y. Yoshii, N. Asami, N. Ienaka and Y. Tsuzuki : Ultraviolet FeII emission in z ~ 2 quasars, Monthly Notices of the Royal Astronomical Society, Vol.395, No.2, 1087-1091, 2009.
(要約)
We present spectra of six luminous quasars at z ~ 2, covering rest wavelengths 1600-3200 ?. The fluxes of the UV FeII emission lines and MgII λ2798 doublet, the line widths of MgII and the 3000 ? luminosity were obtained from the spectra. These quantities were compared with those of low-redshift quasars at z = 0.06-0.55 studied by Tsuzuki et al. In a plot of the FeII(UV)/MgII flux ratio as a function of the central black hole mass, FeII(UV)/MgII in our z ~ 2 quasars is systematically greater than in the low-redshift quasars. We confirmed that luminosity is not responsible for this excess. It is unclear whether this excess is caused by rich Fe abundance at z ~ 2 over low-redshift or by non- abundance effects such as high gas density, strong radiation field and high microturbulent velocity.
M. Negrello, S. Serjeant, C. Pearson, T. Takagi, A. Efstathiou, T. Goto, D. Burgarella, -S. W. Jeong, M. Im, M. H. Lee, H. Matsuhara, Shinki Oyabu, T. Wada and G. White : Photometric redshift accuracy in AKARI deep surveys, Monthly Notices of the Royal Astronomical Society, Vol.394, No.1, 375-397, 2009.
(要約)
We investigate the photometric redshift accuracy achievable with the AKARI infrared data in deep multiband surveys, such as in the North Ecliptic Pole field. We demonstrate that the passage of redshifted polycyclic aromatic hydrocarbons (PAH) and silicate features into the mid-infrared wavelength window covered by AKARI is a valuable means to recover the redshifts of starburst galaxies. To this end, we have collected a sample of ~60 galaxies drawn from the Great Observatories Origins Deep Survey-North Field with spectroscopic redshift 0.5 <~ zspec <~ 1.5 and photometry from 3.6 to 24μm, provided by the Spitzer, Infrared Space Observatory and AKARI satellites. The infrared spectra are fitted using synthetic galaxy spectral energy distributions which account for starburst and active nuclei emission. For ~90 per cent of the sources in our sample, the redshift is recovered with an accuracy |zphot - zspec|/(1 + zspec) <~ 10 per cent. A similar analysis performed on a set of simulated spectra shows that the AKARI infrared data alone can provide photometric redshifts accurate to |zphot - zspec|/(1 + zspec) ~ 10 per cent (1ς) at z <~ 2. At higher redshifts, the PAH features are shifted outside the wavelength range covered by AKARI and the photo-z estimates rely on the less prominent 1.6μm stellar bump; the accuracy achievable in this case on (1 + z) is ~10-15 per cent, provided that the active galactic nuclei contribution to the infrared emission is subdominant. Our technique is no more prone to redshift aliasing than optical-ultraviolet photo-z, and it may be possible to reduce this aliasing further with the addition of submillimetre and/or radio data.
(キーワード)
galaxies: active / galaxies: starburst / infrared: galaxies / Astrophysics
I. Sakon, T. Onaka, T. Wada, Y. Ohyama, H. Kaneda, D. Ishihara, T. Tanab?, T. Minezaki, Y. Yoshii, N. Tominaga, K. Nomoto, T. Nozawa, T. Kozasa, M. Tanaka, T. Suzuki, H. Umeda, Shinki Oyabu, F. Usui, H. Matsuhara, T. Nakagawa and H. Murakami : Properties of Newly Formed Dust by SN 2006JC Based on Near- to Mid-Infrared Observation With AKARI, The Astrophysical Journal, Vol.692, 546, 2009.
(要約)
We present our latest results on near- to mid-infrared (MIR) observation of supernova (SN) 2006jc at 200 days after the discovery using the Infrared Camera (IRC) on board AKARI. The near-infrared (2-5 μm) spectrum of SN 2006jc is obtained for the first time and is found to be well interpreted in terms of the thermal emission from amorphous carbon of 800 ± 10 K with the mass of 6.9 ± 0.5 × 10-5 M sun that was formed in the SN ejecta. This dust mass newly formed in the ejecta of SN 2006jc is in a range similar to those obtained for other several dust-forming core-collapse supernovae based on recent observations (i.e., 10-3-10-5 M sun). MIR photometric data with AKARI/IRC MIR-S/S7, S9W, and S11 bands have shown excess emission over the thermal emission by hot amorphous carbon of 800 K. This MIR excess emission is likely to be accounted for by the emission from warm amorphous carbon dust of 320 ± 10 K with the mass of 2.7+0.7-0.5 × 10-3 M sun rather than by the band emission of astronomical silicate and/or silica grains. This warm amorphous carbon dust is expected to have been formed in the mass-loss wind associated with the Wolf-Rayet stellar activity before the SN explosion. Our result suggests that a significant amount of dust is condensed in the mass-loss wind prior to the SN explosion.
(キーワード)
dust / extinction / infrared: ISM / stars: Wolf-Rayet / supernovae: general / supernovae: individual: SN2006jc / Astrophysics
Satoshi Takita, Yoshimi Kitayama, Hirokazu Kataza, Daisuke Ishihara, Munetaka Ueno, Hideaki Fujiwara, Norio Ikeda, Akiko Kawamurak, Hiroshi Murakami, K. Yoshiko Okamoto, Takashi Onaka, Shinki Oyabu, Itsuki Sakon and Hidenori Takahashi : Diffuse 18 μm Emission around TYC 3159-6-1 Discovered by the AKARI MIR All-Sky Survey, Publications of the Astronomical Society of Japan, Vol.61, No.2, 291-299, 2009.
(要約)
We report on observations of the mysterious object TYC 3159-6-1 located toward the Cygnus X region. It shows interesting characteristics in the AKARI mid-infrared All-Sky Survey. The central star is clearly detected as a point source at 9μ, while no point-like source, but a large shell- like structure is seen around the source at 18μ. The optical spectrum indicates the presence of the weak Hα emission on the red smooth continuum, whereas the mid-infrared N-band spectrum shows neither excess emission nor significant silicate absorption. Interferometric continuum observations at 104GHz do not show any appreciable peak at the position of the star. On the basis of these observations, we investigate three possibilities of concerning the nature of TYC 3159-6-1: a nearby young stellar object, a heavily extincted high-mass star, and an asymptotic giant branch (AGB) star with a detached shell. We conclude that none of these cases can account for the observations consistently, and the nature of TYC 3159-6-1 remains a mystery.
(キーワード)
infrared: ISM / ISM: clouds / stars: individual (TYC 3159-6-1)
Mok Hyung Lee, Jin Seong Kim, Myungshin Im, Hideo Matsuhara, Shinki Oyabu, Takehiko Wada, Takao Nakagawa, Jongwan Ko, Jin Hyun Shim, Gyoon Myung Lee, Narae Hwang, Toshinobu Takagi and Chrisp Pearson : North Ecliptic Pole Wide Field Survey of AKARI: Survey Strategy and Data Characteristics, Publications of the Astronomical Society of Japan, Vol.61, No.2, 375-385, 2009.
(要約)
We present the survey strategy and the data characteristics of the North Ecliptic Pole (NEP) Wide Survey of AKARI. The survey was carried out for about one year starting from 2006 May with 9 passbands from 2.5 to 24μm and the areal coverage of about 5.8degree? centered on NEP. The survey depth reaches to 21.8 AB magnitude near infrared (NIR) bands, and ?18.6 AB magnitude at the mid infrared (MIR) bands such as 15 and 18μm. The total number of sources detected in this survey is about 104000, with more sources in NIR than in the MIR. We have cross matched infrared sources with optically identified sources in CFHT imaging survey which covered about 2degree? within NEP-Wide survey region in order to characterize the nature of infrared sources. The majority of the MIR sources at 15 and 18μm bands are found to be star forming disk galaxies, with smaller fraction of early type galaxies and AGNs. We found that a large fraction (60%--80%) of bright sources in 9 and 11μm is stars while stellar fraction decreases toward fainter sources. We present the histograms of the sources at MIR bands at 9, 11, 15, and 18μm. The number of sources per magnitude thus varies as m0.6 for longer wavelength sources while shorter wavelength sources show steeper variation with m, where m is the AB magnitude.
(キーワード)
infrared: galaxies / photometry / Astrophysics - Astrophysics of Galaxies / Astrophysics - Cosmology and Nongalactic Astrophysics
Shinki Oyabu : A Young Planetary Nebula in the Large Magellanic Cloud near the South Ecliptic Pole, AGB Stars and Related Phenomena, 88, 2009.
157.
D. Ishihara, T. Onaka, H. Fujiwara, I. Sakon, H. Kataza, T. Wada, H. Matsuhara, Shinki Oyabu, Y. Ita, Y. Ohyama, K. Uemizu, S. Hasegawa, I. Yamamura, C. Yamauchi, M. Ueno, S. Takita, H. Shibai, K. Hidehiro, T. Suzuki, Y. Okada and S. Makiuti : AKARI Mid-Infrared All-Sky Survey, The Evolving ISM in the Milky Way and Nearby Galaxies, 30, 2009.
(要約)
AKARI is the first Japanese astronomical infrared satellite mission orbiting around the Earth in a sun-synchronous polar orbit at the altitude of 700 km. One of the major observation programs of the AKARI is an all-sky survey in the mid- to far-infrared spectral regions with 6 photometric bands. The mid-infrared part of the AKARI All-Sky Survey was carried out with the Infrared Camera (IRC) at the 9 and 18 μm bands with the sensitivity of about 50 and 120 mJy (5ς per scan), respectively. The spatial resolution is about 9.''4 at both bands. The 9 μm band probes the UIR bands effectively, whereas the 18 μm band traces the thermal emission from warm dust grains. We present an overview of the mid- infrared all-sky survey and report some initial results to demonstrate its great potential in the study of star-forming regions in our Galaxy.
(キーワード)
infrared : large area survey / reflection nebula : individual (IC 4954/4955) / open clusters : individual (Roslund 4)
158.
Yusei Koyama, Tadayuki Kodama, Kazuhiro Shimasaku, Sadanori Okamura, Masayuki Tanaka, Mok Hyung Lee, Myungshin Im, Hideo Matsuhara, Toshinobu Takagi, Takehiko Wada and Shinki Oyabu : Mapping dusty star formation in and around a cluster at z = 0.81 by wide-field imaging with AKARI, Monthly Notices of the Royal Astronomical Society, Vol.391, No.4, 1758-1770, 2008.
(要約)
We present environmental dependence of dusty star-forming activity in and around the cluster RXJ1716.4+6708 at z = 0.81 based on wide-field and multiwavelength observations with the Prime Focus Camera on the Subaru Telescope (Suprime-Cam) and the Infrared Camera onboard the AKARI satellite. Our optical data show that the optical colour distribution of galaxies starts to dramatically change from blue to red at the medium- density environment such as cluster outskirts, groups and filaments. By combining with the AKARI infrared data, we find that 15-μm-detected galaxies tend to have optical colours between the red sequence and the blue cloud with a tail into the red sequence, consistent with being dusty star-forming galaxies. The spatial distribution of the 15-μm- detected galaxies over ~200 arcmin2 around the cluster reveals that few 15-μm galaxies are detected in the cluster central region. This is probably due to the low star-forming activity in the cluster core. However, interestingly, the fraction of 15-μm-detected galaxies in the medium-density environments is as high as in the low- density field, despite the fact that the optical colours start to change in the medium-density environments. Furthermore, we find that 15-μm- detected galaxies which have optically red colours (candidates for dusty red galaxies) and galaxies with high specific star formation rates are also concentrated in the medium-density environment. These results imply that the star-forming activity in galaxies in groups and filaments is enhanced due to some environmental effects specific to the medium- density environment (e.g. galaxy-galaxy interaction), and such a phenomenon is probably directly connected to the truncation of star- forming activity in galaxies seen as the dramatic change in optical colours in such environment.
Toshihiko TanabÉ, Itsuki Sakon, Martin Cohen, Takehiko Wada, Yoshifusa Ita, Youichi Ohyama, Shinki Oyabu, Kazunori Uemizu, Toshinobu Takagi, Daisuke Ishihara, Woojung Kim, Munetaka Ueno, Hideo Matsuhara and Takashi Onaka : Absolute Photometric Calibration of the Infrared Camera (IRC) aboard AKARI, Publications of the Astronomical Society of Japan, Vol.60, No.sp2, S375-S388, 2008.
(要約)
The absolute photometric calibration of imaging observations with the Infrared Camera (IRC) aboard the AKARI satellite was performed by monitoring the same stars regularly and by observing aset of standard stars. By our monitoring observations, we confirmed that all channels of the IRC were stable to within 4% and that their sensitivities were constant until the liquid helium was exhausted. Using the data of these repeated observations, we evaluated the intrinsic errors as afunction of the brightnesses of objects and found that the errors increase rapidly toward fainter objects. We also checked the consistency between short and long exposure times, and confirmed that the data sampling had been executed as designed. Finally, by comparing the estimated in-band flux densities and the observed data values of standard stars, we obtained conversion factors to the absolute flux densities of all the band/exposure configurations. Their absolute uncertainties are estimated to be less than 6%.
(キーワード)
infrared: general / space vehicles: instruments / techniques: photometric
Takehiko Wada, Hideo Matsuhara, Shinki Oyabu, Toshinobu Takagi, Mok Hyung Lee, Myungshin Im, Youichi Ohyama, Tomotsugu Goto, P. Chris Pearson, J. Glenn White, Stephen Serjeant, Kensuke Wada and Hitoshi Hanami : AKARI/IRC Deep Survey in the North Ecliptic Pole Region, Publications of the Astronomical Society of Japan, Vol.60, No.sp2, S517-S529, 2008.
(要約)
We have made adeep and wide imaging survey with all nine AKARI/IRC bands from 2 to 24 μm within ahalf degree of the North Ecliptic Pole. The survey covered acircular area of 0.38deg2 centered at RA = 17h56m, Dec = 66°37' where adeep optical multi- band survey has been conducted by Subaru/Suprime-Cam. The 5ς sensitivity of the survey for point sources is 11.0, 48, 117, and 275 μJy at wavelengths 3, 7, 15, and 24 μm, respectively. The survey is limited by sky noise at wavelengths from 7 to 24 μm, and limited by source confusion from 2 to 4 μm. We have also made apoint source catalog at each band, consisting of more than 5000 sources with a 50% completeness limit of 93 μ Jy at 15 μm. Our results are consistent with the pilot survey at faint fluxes and has better statistical significance at the bright fluxes. This is the first near- and mid-infrared sub-mJy extragalactic survey with contiguous wavelength coverage from 2 to 24 μm and a large band-merged catalogue. It will provide powerful and unique diagnostics of obscured star-formation and AGN activities in the galaxies up to z = 2.
Tomotsugu Goto, Hitoshi Hanami, Myungshin Im, Koji Imai, Hanae Inami, Tsuyoshi Ishigaki, Mok Hyung Lee, Hideo Matsuhara, Takao Nakagawa, Youichi Ohyama, Shinki Oyabu, P. Chris Pearson, Toshinobu Takagi and Takehiko Wada : Galaxy Clusters at 0.9 < z < 1.7 in the AKARI NEP Deep Field, Publications of the Astronomical Society of Japan, Vol.60, S531, 2008.
(要約)
There is ahuge gap between the properties of red-sequence selected massive galaxy clusters at z < 1 and Lyman-break selected proto- clusters at z > 3. It is important to understand when and how the z > 3 proto-clusters evolve into passive clusters at z < 1. We aim to fill this cluster desert by using space-based N4 (4 μm) imaging with AKARI. The z' - N4 color is apowerful separator of cluster galaxies at z > 1, taking advantage of the 4000? break and the 1.6 μm bump. We carefully selected 16 promising cluster candidates at 0.9 < z < 1.7, which all show an obvious over-density of galaxies and aprominent red-sequence. At this redshift range, the mid-infrared S15μm / S9μm flux ratio is an extinction-free indicator of galaxy star-formation activity due to the redshifted PAH emission lines (6.2, 7.7, and 8.6 μm). We show statistically that the cluster galaxies have alower S15μm / S9μm flux ratio than do field galaxies, i.e., cluster galaxies already have lower star-formation activity at 0.9 < z < 1.7, pushing the formation epoch of these galaxy clusters to a higher redshift.
Y. Matsuoka, A. B. Peterson, Shinki Oyabu, K. Kawara, N. Asami, H. Sameshima, N. Ienaka, T. Nagayama and M. Tamura : Optical to Near-Infrared Spectrum of a Massive Evolved Galaxy at z = 1.26, The Astrophysical Journal, Vol.685, 767, 2008.
(要約)
We present the optical to near-infrared (IR) spectrum of the galaxy TSPS J1329-0957, a red and bright member of the class of extremely red objects (EROs) at z = 1.26. This galaxy was found in the course of the Tokyo-Stromlo Photometry Survey (TSPS) which we are conducting in the southern sky. The spectroscopic observations were carried out with the Gemini Multi-Object Spectrograph (GMOS) and the Gemini Near Infra-Red Spectrograph (GNIRS) mounted on the Gemini-South telescope. The wide wavelength coverage of 0.6-2.3 μm provides useful clues as to the nature of EROs while most published spectra are limited to a narrower spectral range which is dictated by the need for efficient redshift determination in a large survey. We compare our spectrum with several optical composite spectra obtained in recent large surveys, and with stellar population synthesis models. The effectiveness of using near-IR broadband data, instead of the spectral data, in deriving the galaxy properties are also investigated. We find that TSPS J1329-0957 formed when the universe was 2-3 Gyr old, and subsequently evolved passively to become one of the most massive galaxies found in the z = 1-2 universe. Its early type and estimated stellar mass of M* = 1011.5 M? clearly point to this galaxy being a direct ancestor of the brightest elliptical and spheroidal galaxies in the local universe.
M. Shirahata, S. Matsuura, T. Takagi, Shinki Oyabu, H. Matsuhara, T. Nakagawa, M. Kawada, H. Shibai, T. T. Takeuchi, H. Hanami, P. C. Pearson, S. Serjeant and G. White : AKARI Far-Infrared Deep Galaxy Survey, Panoramic Views of Galaxy Formation and Evolution, Vol.399, 290, 2008.
(要約)
The AKARI far-infrared deep survey has been carried out toward the region with the lowest cirrus density in the whole sky, near the South Ecliptic Pole. We present the details of this survey, and show the obtained galaxy counts. More than 2,200 galaxies were detected down to a flux level of 20 mJy, and suggest the necessity for a new model to explain galaxy evolution.
164.
M. Im, M. H. Lee, G. M. Lee, J. Ko, H. Shim, T. Kodama, Y. Koyama, T. Takagi, H. Watarai, H. Matsuhara, T. Wada, Shinki Oyabu and H. Hanami : Evolution of Galaxy Clusters from an AKARI Mission Program, CLEVL, Panoramic Views of Galaxy Formation and Evolution, Vol.399, 382, 2008.
(要約)
We present the status of the AKARI Mission Program on the evolution of cluster of galaxies, CLEVL. In order to understand the evolution of galaxies in cluster environment, we have conducted an AKARI imaging survey of galaxy clusters over a wide redshift range. For 8 low redshift clusters (z < 0.3), we performed 2-24 micron imaging in 6 passbands. For intermediate redshift clusters (0.3 < z < 1.3), we have examined the galaxy properties, and the environmental effect by conducting deep NIR-MIR imaging. For high redshift clusters (z > 1.3), we have imaged fields around radio or submm galaxies looking for signs of over-densities. Our program covers a large scale (?5 Mpc) over each target, enabling us to investigate the interaction of cluster members and its surrounding environment. The multi-wavelength capability enables us to use the same MIR star formation indicator over 0 < z < 3 for a consistent estimate of the star formation rate, and to study dust emission from circumstellar disks.
165.
Y. Matsuoka, Shinki Oyabu and K. Kawara : The State and Evolution of the Partly-Ionized Gas in AGNs Probed with Broad O I and Ca II Emission Lines, Panoramic Views of Galaxy Formation and Evolution, Vol.399, 421, 2008.
(要約)
We are carrying out a program to explore prominent Fe II emission-line regions in AGNs with near-infrared (NIR) O I and Ca II lines as tracers. To date we have observed and compiled the relevant O I (λ1304, λ8446, and λ11287) and Ca II (λ8579 triplet) lines in 11 quasars at 0.06 le z le 1.08. The comparison with photoionization model calculations suggests that gas with a density n_{H} = 1011.5 - 1012.0 cm^{-3} is present in an outer portion of the broad emission-line region (BELR) illuminated by the ionizing radiation whose flux corresponds to the ionization parameter U = 10-3.0 - 10-2.5 on average. While the revealed gas density is similar, the ionizing radiation flux appears to be diverse among the quasars.
166.
Koji Imai, P. Chris Pearson, Hideo Matsuhara, Takehiko Wada, Shinki Oyabu, Toshinobu Takagi, Naofumi Fujishiro and Hitoshi Hanami : Number Density Evolution of Ks-Band-Selected High-Redshift Galaxy Populations in the AKARI North Ecliptic Pole Field, The Astrophysical Journal, Vol.683, 45, 2008.
(要約)
We present the number counts of Ks-band-selected high- redshift galaxy populations such as extremely red objects (EROs), B-, z-, and K-band-selected galaxies (BzKs) and distant red galaxies (DRGs) in the AKARI NEP field. These high-redshift galaxy samples are extracted from a multicolor catalog combining optical data from Suprime-Cam on the 8.2 m Subaru Telescope with near-infrared data from the Florida Multiobject Imaging Near-IR Grism Observational Spectrometer on the Kitt Peak National Observatory 2.1 m telescope over 540 arcmin2 in the NEP region field. The final catalog contains 308 EROs (Ks < 19.0; 54% are dusty star-forming EROs, and the rest are passive old EROs), 137 star-forming BzKs, and 38 passive old BzKs (Ks < 19.0) and 64 DRGs (Ks < 18.6). We also produce individual component source counts for both the dusty star-forming and passive populations. We compare the observed number counts of the high redshift passively evolving galaxy population with a backward pure luminosity evolution (PLE) model allowing different degrees of number density evolution. We find that the PLE model without density evolution fails to explain the observed counts at faint magnitudes, while the model incorporating negative density evolution is consistent with the observed counts of the passively evolving population. We also compare our observed counts of dusty star-forming EROs with a phenomenological evolutionary model postulating that the near-infrared EROs can be explained by the source densities of the far-infrared-submillimeter populations. Our model predicts that the dusty ERO source counts can be explained assuming a 25% contribution of submillimeter star-forming galaxies with the majority of brighter Ks-band-detected dusty EROs having luminous (rather than HR 10 type ultraluminous) submillimeter counterparts. We propose that the fainter Ks > 19.5 population is dominated by the submillijansky submillimeter population. We also predict a turnover in dusty ERO counts around 19 < Ks < 20.
Y. Matsuoka, K. Kawara and Shinki Oyabu : Low-Ionization Emission Regions in Quasars: Gas Properties Probed with Broad O I and Ca II Lines, The Astrophysical Journal, Vol.673, 62, 2008.
(要約)
We have compiled the emission-line fluxes of O I λ8446, O I λ11287, and the near-infrared (IR) Ca II triplet (λ8579) observed in 11 quasars. These lines are considered to emerge from the same gas as do the Fe II lines in the low-ionized portion of the broad emission line region (BELR). The compiled quasars are distributed over wide ranges of redshift (0.06 <= z<= 1.08) and of luminosity (-29.8 <= MB <= - 22.1), thus providing a useful sample to investigate the line-emitting gas properties in various quasar environments. The measured line strengths and velocities, as functions of the quasar properties, are analyzed using photoionization model calculations. We found that the flux ratio between the Ca II triplet and O I λ8446 is hardly dependent on the redshift or luminosity, indicating similar gas densities in the emission region from quasar to quasar. On the other hand, a scatter of the O I λ11287/λ8446 ratios appears to imply the diversity of the ionization parameter. These facts invoke a picture of the line-emitting gases in quasars that have similar densities and are located at regions exposed to various ionizing radiation fluxes. The observed O I line widths are found to be remarkably similar over more than 3 orders of magnitude in luminosity, which indicates a kinematically determined location of the emission region and is in clear contrast to the case of H I lines. We also argue about the dust presence in the emission region since the region is suggested to be located near the dust sublimation point at the outer edge of the BELR.
Narae Hwang, Gyoon Myung Lee, Mok Hyung Lee, Myungshin Im, Taehyun Kim, Hideo Matsuhara, Takehiko Wada, Shinki Oyabu, Soojong Pak, Moo-Young Chun, Hidenori Watarai, Takao Nakagawa, Chris Pearson, Toshinobu Takagi, Hitoshi Hanami and J. Glenn White : An Optical Source Catalog of the North Ecliptic Pole Region, The Astrophysical Journal. Supplement Series, Vol.172, 583-598, 2007.
(要約)
We present a five-band (u*, g', r', i', z') optical photometry catalog of the sources in the north ecliptic pole (NEP) region based on deep observations made with MegaCam at CFHT. The source catalog covers about 2 square degree area centered at the NEP and reaches depths of about 26 mag for u*, g', r' bands, about 25 mag for i' band, and about 24 mag for z' band (4 ς detection over a 1" aperture). The total number of cataloged sources brighter than r'=23 mag is about 56,000 including both point sources and extended sources. From the investigation of photometric properties using the color-magnitude diagrams and color-color diagrams, we have found that the colors of extended sources are mostly (u*-r')<3.0 and (g'-z')>0.5. This can be used to separate the extended sources from the point sources reliably, even for the faint source domain where typical morphological classification schemes hardly work efficiently. We have derived an empirical color-redshift relation of the red sequence galaxies using the Sloan Digital Sky Survey data. By applying this relation to our photometry catalog and searching for any spatial overdensities, we have found two galaxy clusters and one nearby galaxy group. Based on observations obtained with MegaPrime/MegaCam, a joint project of CFHT and CEA/DAPNIA, at the Canada-France-Hawaii Telescope (CFHT), which is operated by the National Research Council (NRC) of Canada, the Institut National des Science de l'Univers of the Centre National de la Recherche Scientifique (CNRS) of France, and the University of Hawaii.
(キーワード)
Catalogs / Galaxies: Clusters: General / Galaxies: General / Galaxies: Photometry / Astrophysics
T. Onaka, H. Matsuhara, T. Wada, N. Fujishiro, H. Fujiwara, M. Ishigaki, D. Ishihara, Y. Ita, H. Kataza, W. Kim, T. Matsumoto, H. Murakami, Y. Ohyama, Shinki Oyabu, I. Sakon, T. TanabÉ, T. Takagi, K. Uemizu, M. Ueno, F. Usui, H. Watarai, M. Cohen, K. Enya, T. Ootsubo, P. C. Pearson, N. Takeyama, T. Yamamuro and Y. Ikeda : The Infrared Camera (IRC) for AKARI -- Design and Imaging Performance, Publications of the Astronomical Society of Japan, Vol.59, No.sp2, S401-S410, 2007.
(要約)
The Infrared Camera (IRC) is one of two focal-plane instruments on the AKARI satellite. It is designed for wide-field deep imaging and low- resolution spectroscopy in the near- to mid-infrared (1.8-26.5'
Yoshifusa Ita, Toshihiko Tanabé, Noriyuki Matsunaga, Yoshikazu Nakada, Mikako Matsuura, Takashi Onaka, Hideo Matsuhara, Takehiko Wada, Naofumi Fujishiro, Daisuke Ishihara, Hirokazu Kataza, Woojung Kim, Toshio Matsumoto, Hiroshi Murakami, Youichi Ohyama, Fumihiko Usui, Shinki Oyabu, Itsuki Sakon, Toshinobu Takagi, Kazunori Uemizu, Munetaka Ueno and Hidenori Watarai : AKARI Observations of Circumstellar Dust in the Globular Clusters NGC 104 and NGC 362, Publications of the Astronomical Society of Japan, Vol.59, No.sp2, S437-S442, 2007.
(要約)
We report on preliminary results of AKARI observations of two globular clusters, NGC 104 and NGC 362. Imaging data covering areas of about 10 F_{7} ratio being greater than unity in NGC 362. Six out of the eight have no 2MASS counterparts. However, we found no such source in NGC 104.
D. Ishihara, T. Onaka, H. Kaneda, T. Suzuki, H. Kataza, I. Sakon, Y. Okada, Y. Doi, N. Fujishiro, H. Fujiwara, Y. Ita, T. Kii, W. Kim, S. Makiuti, T. Matsumoto, H. Matsuhara, H. Murakami, T. Nakagawa, Y. Ohyama, Shinki Oyabu, S. Stephen, H. Shibai, T. Takagi, T. TanabÉ, K. Uemizu, M. Ueno, F. Usui, T. Wada and H. Watarai : AKARI Infrared Imaging of Reflection Nebulae IC4954 and IC4955, Publications of the Astronomical Society of Japan, Vol.59, No.sp2, S443-S454, 2007.
(要約)
We present the observations of the reflection nebulae IC4954 and IC4955 region with the Infrared Camera and the Far-Infrared Surveyor (FIS) on board the infrared astronomical satellite AKARI during its performance verification phase. We obtained 7 band images from 7 to 1601° around the IC4954/4955 region was created from the AKARI mid-infrared All-Sky Survey data. Together with the HI 21cm data, it suggests a large hollow structure of a degree scale, on whose edge the IC4954/4955 region has been created, indicating star formation over three generations in largely different spatial scales.
I. Sakon, T. Onaka, T. Wada, Y. Ohyama, H. Matsuhara, H. Kaneda, Y. Ita, Shinki Oyabu, H. Kataza, N. Fujishiro, C. Ihara, M. Ishigaki, D. Ishihara, W. Kim, Y. Okada, T. Takagi, T. Tanab?, K. Uemizu, M. Ueno, F. Usui, H. Watarai, -C. B. Koo, S. Serjeant, T. Nakagawa, T. Matsumoto and H. Murakami : Properties of UIR Bands in NGC6946 Based on Mid-Infrared Imaging and Spectroscopy with Infrared Camera on Board AKARI, Publications of the Astronomical Society of Japan, Vol.59, No.sp2, S483-S495, 2007.
(要約)
We present results on mid-infrared imaging and spectroscopic observations of the nearby late-type spiral NGC6946 with the Infrared Camera on board AKARI. Based on mid-infrared imaging with the S7 (7μm may be tools to measure the star-formation activity in remote galaxies if these ratios and their variations are well examined and established for a large sample.
Hiroshi Murakami, Hajime Baba, Peter Barthel, L. David Clements, Martin Cohen, Yasuo Doi, Keigo Enya, Elysandra Figueredo, Naofumi Fujishiro, Hideaki Fujiwara, Mikio Fujiwara, Pedro Garcia-Lario, Tomotsugu Goto, Sunao Hasegawa, Yasunori Hibi, Takanori Hirao, Norihisa Hiromoto, Soo Seung Hong, Koji Imai, Miho Ishigaki, Masateru Ishiguro, Daisuke Ishihara, Yoshifusa Ita, Woong-Seob Jeong, Sook Kyung Jeong, Hidehiro Kaneda, Hirokazu Kataza, Mitsunobu Kawada, Toshihide Kawai, Akiko Kawamura, F. Martin Kessler, Do Kester, Tsuneo Kii, Chan Dong Kim, Woojung Kim, Hisato Kobayashi, Chul Bon Koo, Minn Suk Kwon, Mok Hyung Lee, Rosario Lorente, Sin'itirou Makiuti, Hideo Matsuhara, Toshio Matsumoto, Hiroshi Matsuo, Shuji Matsuura, G. Thomas MÜller, Noriko Murakami, Hirohisa Nagata, Takao Nakagawa, Takahiro Naoi, Masanao Narita, Manabu Noda, Hoon Sang Oh, Akira Ohnishi, Youichi Ohyama, Yoko Okada, Haruyuki Okuda, Sebastian Oliver, Takashi Onaka, Takafumi Ootsubo, Shinki Oyabu, Soojong Pak, Yong-Sun Park, P. Chris Pearson, Michael Rowan-Robinson, Toshinobu Saito, Itsuki Sakon, Alberto Salama, Shinji Sato, S. Richard Savage, Stephen Serjeant, Hiroshi Shibai, Mai Shirahata, Jungjoo Sohn, Toyoaki Suzuki, Toshinobu Takagi, Hidenori Takahashi, Toshihiko TanabÉ, T. Tsutomu Takeuchi, Satoshi Takita, Matthew Thomson, Kazunori Uemizu, Munetaka Ueno, Fumihiko Usui, Eva Verdugo, Takehiko Wada, Lingyu Wang, Toyoki Watabe, Hidenori Watarai, J. Glenn White, Issei Yamamura, Chisato Yamauchi and Akiko Yasuda : The Infrared Astronomical Mission AKARI*, Publications of the Astronomical Society of Japan, Vol.59, No.sp2, S369-S376, 2007.
(要約)
AKARI, the first Japanese satellite dedicated to infrared astronomy, was launched on 2006 February 21, and started observations in May of the same year. AKARI has a 68.5 cm cooled telescope, together with two focal-plane instruments, which survey the sky in six wavelength bands from the mid- to far-infrared. The instruments also have the capability for imaging and spectroscopy in the wavelength range 2 - 180 micron in the pointed observation mode, occasionally inserted into the continuous survey operation. The in-orbit cryogen lifetime is expected to be one and a half years. The All-Sky Survey will cover more than 90 percent of the whole sky with higher spatial resolution and wider wavelength coverage than that of the previous IRAS all-sky survey. Point source catalogues of the All-Sky Survey will be released to the astronomical community. The pointed observations will be used for deep surveys of selected sky areas and systematic observations of important astronomical targets. These will become an additional future heritage of this mission.
Shinki Oyabu, T. Wada, Y. Ohyama, H. Matsuhara, T. Takagi, T. Nakagawa, T. Onaka, N. Fujishiro, D. Ishihara, Y. Ita, H. Kataza, W. Kim, T. Matsumoto, H. Murakami, I. Sakon, T. Tanab?, K. Uemizu, M. Ueno, F. Usui, H. Watarai and K. Haze : Detection of an Hα Emission Line on a Quasar, RX J1759.4+6638, at z = 4.3 with AKARI, Publications of the Astronomical Society of Japan, Vol.59, No.sp2, S497-S501, 2007.
(要約)
We report on the detection of an Hα) is consistent with those of previous reports for lower-redshift quasars.
S. Matsuura, M. Shirahata, M. Kawada, Y. Doi, T. Nakagawa, H. Shibai, P. C. Pearson, T. Takagi, -S. W. Jeong, Shinki Oyabu and H. Matsuhara : AKARI Far-Infrared Source Counts in the Lockman Hole, Publications of the Astronomical Society of Japan, Vol.59, No.sp2, S503-S513, 2007.
(要約)
We report initial results of far-infrared observations of the Lockman Hole with Far-Infrared Surveyor onboard the AKARI infrared satellite. On the basis of slow-scan observations of a 0°.6 × 1°.2 contiguous area, we obtained source number counts at 65, 90, and 140 μm counts above 26 mJy account for about 7% of the cosmic background. These results provide strong constraints on the evolutionary scenario, and suggest that the current models may require modifications.
T. Wada, Shinki Oyabu, Y. Ita, H. Matsuhara, P. C. Pearson, T. Onaka, Y. Ohyama, F. Usui, N. Fujishiro, D. Ishihara, H. Kataza, W. Kim, T. Matsumoto, H. Murakami, I. Sakon, T. Tanab?, T. Takagi, K. Uemizu, M. Ueno and H. Watarai : Infrared Camera (IRC) Deep Survey in the Performance-Verification Phase, Publications of the Astronomical Society of Japan, Vol.59, No.sp2, S515-S528, 2007.
(要約)
We report on the first results of a near- and mid-infrared deep survey with the Infrared Camera (IRC) onboard AKARI in the performance- verification phase. Simultaneous observations by the Near-InfraRed (NIR), Mid-InfraRed Short (MIR-S), and Mid-InfraRed Long (MIR-L) channels of the IRC with effective integration times of 4529, 4908, and 4417 seconds at 3, 7, and 15μm raw source counts agrees with those from deep surveys in the GOODS fields, carried out with the Spitzer IRS peak up imager and predictions of current galaxy evolution models. These results indicate that deep surveys with comprehensive wavelength coverage at mid-infrared wavelength are very important to investigate the evolution of infrared galaxies at high redshifts.
M. H. Lee, M. Im, T. Wada, H. Shim, J. S. Kim, G. M. Lee, N. Hwang, H. Matsuhara, T. Nakagawa, Shinki Oyabu, P. C. Pearson, T. Takagi, T. Onaka, N. Fujishiro, H. Hanami, D. Ishihara, Y. Ita, H. Kataza, W. Kim, T. Matusmoto, H. Murakami, Y. Ohyama, I. Sakon, T. TanabÉ, K. Uemizu, M. Ueno, F. Usui and H. Watarai : Nature of Infrared Sources in 11 μm Selected Sample from Early Data of the AKARI North Ecliptic Pole Deep Survey, Publications of the Astronomical Society of Japan, Vol.59, No.sp2, S529-S542, 2007.
(要約)
We present the properties of 11 1012 L? based on detailed modelling of the SEDs. We also find four AGNs lying at various redshifts in the main sample. In addition, we discuss a few sources that have non- typical SEDs of the main sample, including a brown-dwarf candidate, a steep power-law source, a flat-spectrum object, and an early-type galaxy at moderate redshift.
H. Matsuhara, T. Wada, P. C. Pearson, Shinki Oyabu, M. Im, K. Imai, T. Takagi, E. Kang, N. Hwang, -S. W. Jeong, M. H. Lee, G. M. Lee, S. Pak, S. Serjeant, T. Nakagawa, H. Hanami, H. Inami, T. Onaka, N. Fujishiro, D. Ishihara, Y. Ita, H. Kataza, W. Kim, T. Matsumoto, H. Murakami, Y. Ohyama, I. Sakon, T. TanabÉ, K. Uemizu, M. Ueno and H. Watarai : Optical Identification of 15 μm Sources in the AKARI Performance Verification Field toward the North Ecliptic Pole, Publications of the Astronomical Society of Japan, Vol.59, No.sp2, S543-S555, 2007.
(要約)
We present the results of optical identifications for 257 mid-infrared sources detected with a deep 15K_{s}
T. Takagi, H. Matsuhara, T. Wada, Shinki Oyabu, K. Imai, P. C. Pearson, H. Hanami, T. Onaka, N. Fujishiro, D. Ishihara, Y. Ita, H. Kataza, W. Kim, T. Matsumoto, H. Murakami, Y. Ohyama, I. Sakon, T. Tanab?, K. Uemizu, M. Ueno, H. Watarai, F. Usui, M. H. Lee, M. Im, S. Serjeant, S. R. Savage, T. Tange and T. Nakagawa : Multi-Wavelength Analysis of 18 μm-Selected Galaxies in the AKARI/Infrared-Camera monitor fieldtowards the North Ecliptic Pole, Publications of the Astronomical Society of Japan, Vol.59, No.sp2, S557-S569, 2007.
(要約)
We present an initial analysis of AKARI 18z Ultra-Luminous InfraRed Galaxies, and a large variation of the PAH inter-band strength ratio in galaxies at high redshifts.
Y. Matsuoka, Shinki Oyabu, Y. Tsuzuki and K. Kawara : State and evolution of the partly ionized gas in AGNs, Il Nuovo Cimento B / Il Nuovo Cimento B Series 10, Vol.122, No.9-11, 1273-1276, 2007.
(要約)
Physical parameters of galaxies (as luminosity, stellar mass, age) are often derived by means of the model templates which best fit their spectro-photometric data. We have performed a quantitative test aimed at exploring the ability of this procedure in recovering the physical parameters of early-type galaxies at 1<z<2. A wide range of simulated SEDs, reproducing those of early-type galaxies at 1<z<2 with assigned age and mass, are used to build mock photometric catalogs with wavelength coverage and photometric uncertainties similar to those of two topical surveys (i.e. VVDS and GOODS). The best fitting analysis of the simulated photometric data allows to study the differences among the recovered parameters and the input ones. Results indicate that the stellar masses measured by means of optical bands are affected by larger uncertainties with respect to those obtained from near-IR bands, and they frequently underestimate the real values. The M/L ratio in the V band results strongly underestimated, even when derived from the recently proposed recipe based on rest-frame optical colours (e.g. (B-V)).
Y. Matsuoka, Shinki Oyabu, Y. Tsuzuki and K. Kawara : Observations of O I and Ca II Emission Lines in Quasars: Implications for the Site of Fe II Line Emission, The Astrophysical Journal, Vol.663, 781, 2007.
(要約)
We present results of the near-infrared (IR) spectroscopy of six quasars whose redshifts range from 0.158 to 1.084. Combined with the satellite ultraviolet data, the relative line strengths of O I λ1304, O I λ8446, O I λ11287, and the near-IR Ca II triplet are given. In addition, the corresponding O I line strengths measured in normal Seyfert 1s and narrow-line Seyfert 1s are collected from the literature. These lines are thought to emerge from the same gas as do the Fe II lines, so they are good tracers of the Fe II emission region within a broad emission line region (BELR) in active galactic nuclei (AGNs). In order to reveal the physical condition within the relevant emission region, we performed photoionized model calculations and compared them to the observations. It suggests that a rather dense gas with density nH~1011.5 cm-3 is present at an outer portion of the BELR, illuminated by the ionizing radiation corresponding to an ionization parameter U~10-2.5 and is primarily responsible for the observed O I, Ca II, and Fe II lines, based on the resemblance of their profiles. The three O I lines are proven to be formed through Lyβ fluorescence and collisional excitation. We also show that the λ1304 bump typically observed in AGN spectra consists of the comparable contributions of O I and Si II multiplets, and we discuss the origin of such a strong Si II emission. The results are interpreted in the context of the locally optimally emitting cloud (LOC) scenario to find the plausible gas distribution within the BELR as a function of distance from the central source and density.
Koji Imai, Hideo Matsuhara, Shinki Oyabu, Takehiko Wada, Toshinobu Takagi, Naofumi Fujishiro, Hitoshi Hanami and P. Chris Pearson : J- and Ks-Band Galaxy Counts and Color Distributions in the AKARI North Ecliptic Pole Field, The Astronomical Journal, Vol.133, No.5, 2418, 2007.
(要約)
We present the J- and Ks-band galaxy counts and galaxy colors covering 750 arcmin2 in the deep AKARI north ecliptic pole (NEP) field, using the Florida Multi-object Imaging Near-IR Grism Observational Spectrometer on the Kitt Peak National Observatory 2.1 m telescope. The limiting magnitudes with a signal-to-noise ratio of 3 in the deepest regions are 21.85 and 20.15 in the J and Ks bands, respectively, in the Vega magnitude system. The J- and Ks-band galaxy counts in the AKARI NEP field are broadly in good agreement with those of other results in the literature; however, we find some indication of a change in the galaxy number count slope at J~19.5 and over the magnitude range 18.0<Ks<19.5. We interpret this feature as a change in the dominant population at these magnitudes because we also find an associated change in the B-Ks color distribution at these magnitudes, where the number of blue samples in the magnitude range 18.5<Ks<19.5 is significantly larger than that of Ks<17.5.
Glenn White, Kotaro Kohno, Hideo Matsuhara, Shuji Matsuura, Hitoshi Hanami, Mok Hyung Lee, Chris Pearson, Toshi Takagi, Stephen Serjeant, Woongseob Jeong, Shinki Oyabu, Mai Shirahata, Kouichiro Nakanishi, Elysandra Figueredo and Mireya Etxaluze : Observing the Birth and evolution of Galaxies - the ATCA-AKARI-ASTE/AzTEC deep South Ecliptic Pole Field, ATNF Proposal, C1697, 2007.
(要約)
We propose deep 20 cm observations supporting the AKARI (3-160 micron)/ASTE/AzTEC (1.1 mm) SEP ultra deep ('Oyabu Field') survey of an extremely low cirrus region at the South Ecliptic Pole. Our combined IR/mm/Radio survey addresses the questions: How do protogalaxies and protospheroids form and evolve? How do AGN link with ULIRGs in their birth and evolution? What is the nature of the mm/submm extragalactic source population? We will address these by sampling the star formation history in the early universe to at least z~2. Compared to other Deep Surveys, a) AKARI multi-band IR measurements allow precision photo-z estimates of optically obscured objects, b) our multi-waveband contiguous area will mitigate effects of cosmic variance, c) the low cirrus noise at the SEP (< 0.08 MJy/sr) rivals that of the Lockman Hole "Astronomy's other ultra-deep 'cosmological window'", and d) our coverage of four FIR bands will characterise the far-IR dust emission hump of our starburst galaxies better than SPITZER's two MIPS bands allow. The ATCA data are crucial to galaxy identification, and determining the star formation rates and intrinsic luminosities through this unique Southern cosmological window.
(キーワード)
Extragalactic / ATCA
185.
Yumihiko Tsuzuki, Kimiaki Kawara, Yuzuru Yoshii, Shinki Oyabu, Toshihiko Tanabé and Yoshiki Matsuoka : Fe II Emission in 14 Low-Redshift Quasars. I. Observations, The Astrophysical Journal, Vol.650, No.1, 57, 2006.
(要約)
We present the spectra of 14 quasars with a wide coverage of rest wavelengths from 1000 to 7300 ?. The redshift ranges from z=0.061 to 0.555 and the luminosity from MB=-22.69 to -26.32. These spectra of high quality result from combining Hubble Space Telescope spectra with those taken from ground-based telescopes. We describe the procedure of generating the template spectrum of Fe II line emission from the spectrum of a narrow-line Seyfert 1 galaxy, I Zw 1, that covers two wavelength regions of 2200-3500 and 4200-5600 ?. Our template Fe II spectrum is semiempirical in the sense that the synthetic spectrum calculated with the CLOUDY photoionization code is used to separate the Fe II emission from the Mg II λ2798 line. The procedure of measuring the strengths of Fe II emission lines is twofold: (1) subtracting the continuum components by fitting models of the power-law and Balmer continua in the continuum windows, which are relatively free from line emissions, and (2) fitting models of the Fe II emission based on the Fe II template to the continuum-subtracted spectra. From 14 quasars including I Zw 1, we obtained the Fe II fluxes in five wavelength bands (U1 [2200-2660 ?], U2 [2660-3000 ?], U3 [3000-3500 ?], O1 [4400-4700 ?], and O2 [5100-5600 ?]), the total flux of Balmer continuum, and the fluxes of Mg II λ2798, Hα, and other emission lines, together with the full widths at half-maximum (FWHMs) of these lines. Regression analysis was performed by assuming a linear relation between any two of these quantities. Eight correlations were found with a confidence level higher than 99%: (1) larger Mg II FWHM for larger Hα FWHM, (2) larger Γ for fainter MB, (3) smaller Mg II FWHM for larger Γ, (4) larger Mg II FWHM for smaller Fe II(O1)/Mg II, (5) larger MBH for smaller Γ, (6) larger MBH for smaller Fe II(O1)/Mg II, (7) larger [O III]/Hβ for larger Mg II FWHM, and (8) larger Fe II(O1)/Mg II for larger Fe II(O1)/Fe II(U1). The fact that six of these eight are related to FWHM or MBH (~FWHM2) may imply that MBH is a fundamental quantity that controls Γ or the spectral energy distribution (SED) of the incident continuum, which in turn controls the Fe II emission. Furthermore, it is worthy of noting that Fe II(O1)/Fe II(U1) is found to tightly correlate with Fe II(O1)/Mg II, but not with Fe II(U1)/Mg II.
(キーワード)
Galaxies: Abundances / Galaxies: Active / Galaxies: Individual: Alphanumeric: I Zw 1 / Methods: Data Analysis / Galaxies: Quasars: Emission Lines / Astrophysics
Hideo Matsuhara, Takehiko Wada, Shuji Matsuura, Takao Nakagawa, Mitsunobu Kawada, Youichi Ohyama, P. Chris Pearson, Shinki Oyabu, Toshinobu Takagi, Stephen Serjeant, J. Glenn White, Hitoshi Hanami, Hidenori Watarai, T. Tsutomu Takeuchi, Tadayuki Kodama, Nobuo Arimoto, Sadanori Okamura, Mok Hyung Lee, Soojong Pak, Shin Myung Im, Gyoon Myung Lee, Woojung Kim, Woong-Seob Jeong, Koji Imai, Naofumi Fujishiro, Mai Shirahata, Toyoaki Suzuki, Chiaki Ihara and Itsuki Sakon : Deep Extragalactic Surveys around the Ecliptic Poles with AKARI (ASTRO-F), Publications of the Astronomical Society of Japan, Vol.58, No.4, 673-694, 2006.
(要約)
AKARI (formerly ASTRO-F) is an infrared space telescope designed for an all-sky survey at 10-180 μm, and deep pointed surveys of selected areas at 2-180 μm. The deep pointed surveys with AKARI will significantly advance our understanding of galaxy evolution, the structure formation of the universe, the nature of buried AGNs, and the cosmic infrared background. We describe here the important characteristics of the AKARI mission, the orbit, and attitude control system, and investigate the optimum survey area based on the updated pre-flight sensitivities of AKARI, taking into account the cirrus confusion noise as well as the surface density of bright stars. The North Ecliptic Pole is concluded to be the best area for 2-26μm deep surveys, while the low-cirrus noise regions around the South Ecliptic Pole are worth considering for 50-180μm pointed surveys to high sensitivities limited by the galaxy confusion noise. Current observational plans concerning these pointed surveys are described in detail. Comparing these surveys with deep surveys using the Spitzer Space Telescope, the AKARI deep surveys are particularly unique in respect of their continuous wavelength coverage over the 2-26μm range in broad-band deep imaging, and their slitless spectroscopy mode over the same wavelength range.
Shinki Oyabu, S. Min Yun, T. Murayama, B. D. Sanders, K. Kawara, Y. Taniguchi, S. Veilleux, H. Okuda, H. Matsuhara, L. L. Cowie, Y. Sato, K. Wakamatsu and Y. Sofue : Optical Identification of Infrared Space Observatory Far-Infrared Sources in the Lockman Hole Using a Deep Very Large Array 1.4 GHz Continuum Survey, The Astronomical Journal, Vol.130, No.5, 2019, 2005.
(要約)
By exploiting the far-infrared (FIR) and radio correlation, we have performed a likelihood-ratio analysis to identify optical counterparts to the FIR sources that have been found in an area of ~0.9 deg2 during the Infrared Space Observatory (ISO) deep FIR survey in the Lockman Hole. New ground-based observations have been conducted to build up the catalogs of radio and optical objects, which include a deep Very Large Array (VLA) observation at 1.4 GHz, optical R- and I-band imaging with the Subaru 8 m and University of Hawaii 2.2 m telescopes, and optical spectroscopy with the Keck II 10 m and WIYN 3.5 m telescopes. This work is based on FIR samples consisting of 116 and 20 sources selected with the criteria of FC(90 μm)>=43 mJy and FC(170 μm)>=102 mJy, respectively, where FC is the bias-corrected flux. Using the likelihood ratio analysis and the associated reliability, 44 FIR sources have been identified with radio sources. Optical confirmation of the 44 FIR/radio associations was then conducted using accurate radio positions. Redshifts have been obtained for 29 out of the 44 identified sources. One hyperluminous infrared galaxy (HyLIRG) with LFIR>1013 Lsolar and four ultraluminous infrared galaxies (ULIRGs) with LFIR=1012-1013 Lsolar are identified in our sample, while the remaining 24 FIR galaxies have LFIR<1012 Lsolar. The space density of the FIR sources at z=0.3-0.6 is 4.6×10-5 Mpc-3, which is 460 times larger than the local value, implying a rapid evolution of the ULIRG population. Most ISO FIR sources have L(1.4 GHz)/L(90 μm) similar to the star-forming galaxies Arp 220 and M82, indicating that star formation is the dominant mechanism for their FIR and radio luminosity. At least seven of our FIR sources show evidence for the presence of an active galactic nucleus (AGN) in optical emission lines, radio continuum excess, or X-ray activity. Three out of five (60%) of the ULIRGs/HyLIRGs are AGN galaxies, suggesting that the AGN fraction among the ULIRG/HyLIRG population may not change significantly between z~0.5 and the present epoch. Five of the seven AGN galaxies are within the ROSAT X-ray survey field, and two are within the XMM-Newton survey fields. X-ray emission has been detected in only one source, 1EX030, which is optically classified as a quasar. The nondetection in the XMM-Newton 2-10 keV band suggests a very thick absorption column density of 3×1024 cm-2 or AV~1200 mag obscuring the central source of the two AGN galaxies. Several sources have an extreme FIR luminosity relative to the optical R band, L(90 μm)/L(R)>500, which is rare even among the local ULIRG population. While source confusion or blending might offer an explanation in some cases, these observations may represent a new population of galaxies with an extreme amount of star formation in an undeveloped stellar system, i.e., formation of bulges or young elliptical galaxies.
Yoshiki Matsuoka, Shinki Oyabu, Yumihiko Tsuzuki, Kimiaki Kawara and Yuzuru Yoshii : On I Line Emission in the Quasar PG 1116+215, Publications of the Astronomical Society of Japan, Vol.57, No.4, 563, 2005.
(要約)
By observing the near-infrared spectrum of the quasar PG 1116+215 at z = 0.176 and combining with the HST/FOS spectrum, we obtained the relative strengths of three permitted O I lines (λ1304, λ8446, and λ11287) in a quasar for the first time. The photon flux ratios of the O I lines of the quasar were compared with those previously measured in a Seyfert 1 and six narrow-line Seyfert 1s. No significant differences were found in the O I line flux ratios between the quasar and the other Seyferts, suggesting that the gas density in the O I and Fe II line-emitting regions in the quasar is of the same order as those in low-luminosity AGNs. It was also found that the line width of O I λ11287 is significantly narrower than that of Lyα, which is consistent with O I and Fe II emission occurring in the partly ionized regions at the outermost portion of the broad-line region where velocities are small.
K. Kawara, H. Matsuhara, H. Okuda, Y. Taniguchi, Y. Sato, Y. Sofue, K. Wakamatsu, Shinki Oyabu, B. D. Sanders and L. L. Cowie : ISO deep far-infrared survey in the ``Lockman Hole''. III. Catalogs and source counts at 90 & 170 μm, Astronomy & Astrophysics, Vol.413, No.3, 843-859, 2004.
(要約)
We present the catalogs and source counts for the C90 (reference wavelength of 90 μm) and C160 (170 μm) bands, which were extracted from our analysis of an ISO deep far-infrared survey conducted as part of the Japan/UH ISO cosmology project. The total survey area is ?0.9 deg2 in two fields within the Lockman Hole. The analysis consists of source extraction using the IRAF DAOPHOT package and simulations carried out by adding artificial sources to the maps to estimate the detection rate, the flux bias, the positional accuracy, and the noise. The flux calibration was performed using the Sb galaxy UGC 06009 - the photometric error was estimated to be ?50% at C90 and ?65% at C160. The total noise estimated from the simulation is dominated by the confusion noise due to the high source density. The confusion noise is ?20 mJy at C90 and ?35 mJy at C160, which is much larger than the instrumental noise which is at the level of a few mJy or less. The catalogs were constructed by selecting 223 C90 sources and 72 C160 sources with a Signal to Noise Ratio (SNR) of three or greater. The distribution of the observed associations between C90 and C160 sources indicates that the 1 ς positional errors are ?20 arcsec and ?35 arcsec at C90 and C160, respectively. The corrections for the detection rate and the flux bias are significant for sources fainter than 200 mJy at C90 and 250 mJy at C160. Most of the sources detected both at C90 and C160 have a F(C160)/F(C90) color redder than the Sb galaxy UGC 06009. Such a red color could result from reddening due to the flux bias or a K-correction brightening due to the effect of redshift. Red sources brighter than 200 mJy at C160 may be very luminous galaxies like Arp 220 at moderate redshift. The source counts are derived by applying the corrections for the detection rate and flux bias. The resultant counts are quite consistent with the constraints derived from the fluctuation analysis performed in Paper II. The C160 counts are also consistent with the results from the FIRBACK project. Our C90 survey, which is 2-3 times deeper than those previously published, reveals an upturn in the count slope at around 200 mJy. While recent models give a reasonable fit to the C160 counts, none of them are successful in accounting for the upturn in the C90 counts. If the upturn is caused by ultraluminous IR galaxies, their redshifts would need to be at z ? 0.5, implying a major event in galaxy evolution at moderate redshift. Based on observations with ISO, an ESA project with instruments funded by ESA member states (especially the PI countries: France, Germany, The Netherlands, and the UK) and with the participation of ISAS and NASA.
S. M. Yun, Shinki Oyabu, K. Kawara, H. Okuda, D. Sanders, S. Veilleux, T. Murayama and Y. Taniguchi : Radio and FIR Sources in the Lockman Hole ISOPHOT Survey Field, Revista Mexicana de Astronomia y Astrofisica Conference Series, Vol.17, 271, 2003.
(要約)
To investigate the nature and the evolution of optically faint, luminous infrared starburst galaxies, a deep survey of two 44'×44' fields in the Lockman Hole region was conducted using ISOPHOT camera on ISO at 95 and 175 mu m (Kawara et al. 1998). We present the preliminary results from our multi-wavelength investigations of the identified sources in the Lockman Hole ROSAT/XMM deep field (de Ruiter et al. 1997, Hasinger et al. 2001). One or more radio sources are found at the source position in more than 80% of cases, and spectroscopic redshifts of about 50% of the sources have been obtained so far.
Yasuhiro Shioya, Yoshiaki Taniguchi, Takashi Murayama, Masaru Ajiki, Tohru Nagao, S. Shinobu Fujita, Yuko Kakazu, Yutaka Komiyama, Sadanori Okamura, Shinki Oyabu, Kimiaki Kawara, Youichi Ohyama, S. Koji Kawabata, Hiroyasu Ando, Tetsuo Nishimura, Masahiko Hayashi, Ryusuke Ogasawara and Shin-Ichi Ichikawa : SDSSp J104433.04?012502.2 at z=5.74 is Gravitationally Magnified by an Intervening Galaxy, Publications of the Astronomical Society of Japan, Vol.54, No.6, 975-979, 2002.
(要約)
During the course of our optical deep survey program on Lα emitters at z ? 5.7 in the sky area surrounding the quasar SDSSp J104433.04 012502.2 at z = 5.74, we found that a faint galaxy with mB(AB) ? 25 is located at 1."9 southwest of the quasar. Its broad-band color properties from B to z' suggest that the galaxy is located at a redshift of z ? 1.5 2.5. This is consistent with no strong emission line in our optical spectroscopy. Since the counter-image of the quasar cannot be seen in our deep optical images, the magnification factor seems not to be very high. Our modest estimate is that this quasar is gravitationally magnified by a factor of 2.
Masaru Ajiki, Yoshiaki Taniguchi, Takashi Murayama, Tohru Nagao, Sylvain Veilleux, Yasuhiro Shioya, S. Shinobu Fujita, Yuko Kakazu, Yutaka Komiyama, Sadanori Okamura, B. David Sanders, Shinki Oyabu, Kimiaki Kawara, Youichi Ohyama, Masanori Iye, Nobunari Kashikawa, Michitoshi Yoshida, Toshiyuki Sasaki, George Kosugi, Kentaro Aoki, Tadafumi Takata, Yoshihiko Saito, S. Koji Kawabata, Kazuhiro Sekiguchi, Kiichi Okita, Yasuhiro Shimizu, Motoko Inata, Noboru Ebizuka, Tomohiko Ozawa, Yasushi Yadoumaru, Hiroko Taguchi, Hiroyasu Ando, Tetsuo Nishimura, Masahiko Hayashi, Ryusuke Ogasawara and Shin-ichi Ichikawa : A New High-Redshift Lyα Emitter: Possible Superwind Galaxy at z=5.69, The Astrophysical Journal, Vol.576, L25, 2002.
(要約)
During the course of our deep optical imaging survey for Lyα emitters at z~5.7 in the field around the z=5.74 quasar SDSSp J104433.04-012502.2, we found a candidate strong emission line source. Follow-up optical spectroscopy shows that the emission-line profile of this object is asymmetric, showing excess red wing emission. These properties are consistent with an identification of Lyα emission at a redshift of z=5.687+/-0.002. The observed broad line width (?vFWHM~=340 km s-1) and excess red wing emission also suggest that this object hosts a galactic superwind. Based on data collected at the Subaru Telescope, which is operated by the National Astronomical Observatory of Japan, and at the W. M. Keck Observatory.
Shinki Oyabu, K. Kawara, Y. Tsuzuki, Y. Sofue, Y. Sato, H. Okuda, Y. Taniguchi, H. Shibai, C. Gabriel, T. Hasegawa and E. Nishihara : ISO continuum observations of quasars at z=1-4. I. Spectral energy distributions of quasars from the UV to far-infrared, Astronomy & Astrophysics, Vol.365, No.3, 409-416, 2001.
(要約)
Eight luminous quasars with -30 < MB < -27 at z = 1.4-3.7 have been observed in the mid- and far-infrared using ISO. All the quasars have been detected in the mid-infrared bands of ISOCAM, while no far-infrared detections have been made with ISOPHOT. SEDs (Spectral Energy Distributions) from the UV to far-infrared have been obtained while supplementing ISO observations with photometry in the optical and near-infrared made from the ground within 17 months. The SEDs are compared with the MED (Mean spectral Energy Distributions) of low-redshift quasars with -27 < MB < -22. It is shown that our far-infrared observations were limited by confusion noise due to crowded sources. The observations reported here were made with ISO, an ESA project with instruments funded by ESA member states (especially the PI countries: France, Germany, The Netherlands, and the UK) and with the participation of ISAS and NASA, and with the facilities at the Cerro Tololo Inter-american Observatory (CTIO), NOAO, which is operated by AURA, Inc., under contract with NSF, at the Kiso Observatory, which is operated by Institute of Astronomy, the University of Tokyo, and at the Okayama Astrophysical Observatory, the National Astronomical Observatory of Japan.
B. David Sanders, Sylvain Veilleux, Min Yun, L. Lennox Cowie, Kimiaki Kawara, Yoshiaki Taniguchi, Shinki Oyabu, Takashi Murayama and Haruyuki Okuda : Identification of ISOPHOT Deep Field Sources, Starburst Galaxies: Near and Far, 297, 2001.
195.
Shinki Oyabu, K. Kawara, Y. Tsuzuki, Y. Sofue, Y. Sato, H. Okuda, Y. Taniguchi, H. Shibai, C. Gabriel, T. Hasegawa and E. Nishihara : ISO Continuum Observations of Quasars at z=1-4, Institute of Space and Astronautical Science Report, Vol.14, 139, 2000.
(要約)
Eight luminous quasars with -30 < MB < -27 at z = 1.4 - 3.7 have been observed in the mid- and far-infrared with ISO. To obtain SEDs (Spectral observed in the mid- and far-infrared with ISO. To obtain spectral energy distributions (SEDs) from the UV to far-infrared, additional optical and near-infrared observations were made from the ground. The observed SEDs are compared with the mean-SED of low-redshift quasars with less luminosity (-27 < MB < -22) given by Elvis et al. (1994). There is no evidence of excess in the mid- and far- infrared in our quasar sample.
(キーワード)
QUASARS / ISO / INFRARED ASTRONOMY / SPECTRAL ENERGY DISTRIBUTIONS
SMI (SPICA Mid-infrared Instrument) is one of the three focal-plane science instruments for SPICA. SMI is the Japanese-led instrument proposed and managed by a university consortium. SMI covers the wavelength range from 10 to 36 μm with four separate channels: the low-resolution (R = 60 - 160) spectroscopy function for 17 - 36 μm, the broad-band (R = 5) imaging function at 34 μm, the mid-resolution (R = 1400 - 2600) spectroscopy function for 18 - 36 μm, and the high-resolution (R = 29000) spectroscopy function for 10 - 18 μm. In this presentation, we will show the latest design and specifications of SMI as a result of feasibility studies.
Hiroshi Maeshima, Kosei Matsumoto, Yasuhiro Hirahara, Takao Nakagawa, Takehiko Wada, Koichi Nagase, Shinki Oyabu, Toyoaki Suzuki, Takuma Kokusho, Hidehiro Kaneda, Ryota Ito and Daichi Ishikawa : Transmittance measurement of low/high-resistivity of CdZnTe at cryogenic temperature for material selection of the immersion grating of SPICA SMI, Proceedings of SPIE, Vol.11451, 114515X-10, 2020.
(要約)
We measured the transmittance of low-resistivity (∼ 10^2 Ωcm) and high-resistivity (> 10^10 Ωcm) CdZnTe, which are candidates for Immersion grating (IG) in 10-18μm wavelength, at cryogenic temperature. IG is a compact diffraction grating and we are developing a cryogenically operated 10--18μm IG for SMI/HR (SPICA Mid-Infrared Instrument / High-Resolution spectrometer) of SPICA (SPace Infrared telescope for Cosmology and Astrophysics) We performed two experiments: transmittance measurement with a convergent light Fourier transform spectrometer, and with a collimated lamp beam system. Our result shows that the low-resistivity CdZnTe has large absorption (> 0.5 cm^{-1} ) and the high-resistivity CdZnTe has low absorption (< 0.1 cm^{-1} ) at 8.5K at 10--18 μm. The high-resistivity CdZnTe is promising as an IG material although higher precision measurement is needed to determine whether it meets the absorption coefficient requirement (< 0.01 cm^{-1}) at cryogenic temperature.
Tímea Kovács, Denis Burgarella, Hidehiro Kaneda, Molnár Cs. Dániel, Shinki Oyabu, Sandor Pinter and L. Toth Viktor : PAHs and star formation in ELAIS N1 as seen by AKARI, Uncovering Early Galaxy Evolution in the ALMA and JWST Era, Vol.352, 241-242, 2020.
(要約)
We have examined the relationship between star formation and polycyclic aromatic hydrocarbons (PAHs) by fitting the spectral energy distributions (SED) of AKARI selected galaxies. PAHs are excited by the ultraviolet (UV) photons of young stars and can trace star formation in galaxies, but they are disassociated by the strong UV radiation in starbursts. AKARI covered the mid-infrared, where the PAHs emit their radiation, with a high density of photometric bands. These observations allow us to estimate the star formation rate and the PAH mass fraction of the dust in galaxies. In the future the James Webb Space Telescope (JWST) will also make measurements in this wavelength range. This research can therefore be considered as a pathfinder to similar studies that will come later from JWST observations.
(キーワード)
galaxies: ISM / galaxies: star formation / infrared: galaxies
SMI (SPICA Mid-infrared Instrument) is one of the two focal-plane science instruments for SPICA. SMI is the Japanese led instrument proposed and managed by a nation-wide university consortium in Japan and planned to be developed in collaboration with Taiwan and the US. SMI covers the wavelength range from 12 to 36 μm with 4 separate channels: the low-resolution (R = 50-120) spectroscopy function for 17-36 μm, the broad-band (R = 5) imaging function at 34 μm, the mid-resolution (R = 1300-2300) spectroscopy function for 18-36 μm, and the high-resolution (R = 28000) spectroscopy function for 12-18 μm. In this paper, we show the results of our conceptual design and feasibility studies of SMI.
Akino Kondo, Hidehiro Kaneda, Misato Fukagawa, Toyoaki Suzuki, L. Katsuhiro Murata, Takuma Kokusho and Shinki Oyabu : Processing of hydrocarbon dust in star-forming galaxies revealed with AKARI, The Cosmic Wheel and the Legacy of the AKARI Archive: From Galaxies and Stars to Planets and Life, 115, 2018.
(要約)
Hydrocarbon dust is one of the dominant components of interstellar dust, which mainly consists of polycyclic aromatic hydrocarbons and aliphatic hydrocarbons. While hydrocarbon dust is thought to be processed in interstellar radiation fields or shocks, detailed processing mechanisms are not completely understood yet. Therefore, we study the infrared spectral properties of hydrocarbon dust for 138 pure star-forming galaxies at redshift z less than 0.3. Using near-infrared spectra (2.5-5 micrometers) obtained with AKARI/IRC, we derived the luminosities of the aromatic hydrocarbon feature at 3.3 micrometers(L(sub aromatic)) and the aliphatic hydrocarbon feature at 3.4-3.6 micrometers (L(sub aliphatic)). We also derived the total infrared luminosity (L(sub IR)), the total PAH luminosity (L(sub PAH)) and the radiation field strength by modeling the spectral energy distributions of the sample galaxies with AKARI, IRAS, and WISE photometry data. We find that L(sub aliphatic)/L(sub IR) decreases with L(sub IR), like L(sub PAH)/L(sub IR) shown in previous studies. Moreover, we find that L(sub aliphatic)/L(sub aromatic) decreases with L(sub IR), indicating that aliphatic hydrocarbons are more highly processed than aromatic hydrocarbons. In this paper, we discuss possible processing mechanisms of interstellar hydrocarbon dust in galaxies with higher L(sub IR).
(キーワード)
infrared: ISM / galaxies: star formation / ISM: dust
Yoichi Oyama, Takehiko Wada, Hideo Matsuhara, Toshinobu Takagi, M. Malkan, Tomotsugu Goto, Eiichi Egami, Mok Hyung Lee, Myung Im, -H. J. Kim, Chris Pearson, Hanae Inami, Shinki Oyabu, Fumihiko Usui, Denis Burgarella, F. Mazyed, Masatoshi Imanishi, Woong-Seob Jeong, Takamitsu Miyaji, J. DiazTello and Takao Nakagawa : AKARI MIR slitless spectroscopic survey of galaxies at z less than 0.5, The Cosmic Wheel and the Legacy of the AKARI Archive: From Galaxies and Stars to Planets and Life, 359, 2018.
(要約)
We aim to study star-forming galaxies by using a blind spectroscopic survey at mid-infrared (MIR) wavelengths to understand evolution of their star formation rate (SFR) and specific SFR (SFR per stellar mass) up to z in the order of 0.5, by paying particular attention to their Polycyclic Aromatic Hydrocarbon (PAH) properties. We conducted a low- resolution (R approximately equal to 50) slitless spectroscopic survey at 5-13 micrometers of 9 micrometers flux-selected sources (approximately greater than 0.3 mJy) around the North Ecliptic Pole with the Infrared Camera (IRC) onboard AKARI. We identified 48 PAH galaxies with PAH 6.2, 7.7, and 8.6 micrometers features at z approximately less than 0.5. The rest-frame optical-MIR spectral energy distributions (SEDs) based on CFHT and AKARI/IRC imaging are produced and analyzed in conjunction with the PAH spectroscopy. The rest-frame SEDs of all PAH galaxies have a universal shape with stellar and 7.7 micrometers (PAH) bumps, except that the PAH enhancement (luminosity ratio of the 7.7 micrometers PAH feature over the 3.5 micrometers stellar bump) significantly varies as a function of the PAH luminosities. We identified a PAH-enhanced population at z approximately less than 0.35, whose SEDs and luminosities are typical of luminous infrared galaxies. They show particularly larger PAH enhancement at high luminosity, implying that they are vigorous star-forming galaxies with elevated specific SFR. Our composite starburst model that combines a young and dusty starburst with a very old population can successfully reproduce most SED characteristics.
Naofumi Fujishiro, Hirokazu Kataza, Takehiko Wada, Yuji Ikeda, Itsuki Sakon and Shinki Oyabu : Free-form reflective optics for mid-infrared camera and spectrometer on board SPICA, Society of Photo-Optical Instrumentation Engineers (SPIE) Conference Series, Vol.10564, 105640G, 2017.
(要約)
SPICA (Space Infrared Telescope for Cosmology and Astrophysics) is an astronomical mission optimized for mid-and far-infrared astronomy with a cryogenically cooled 3-m class telescope, envisioned for launch in early 2020s. Mid-infrared Camera and Spectrometer (MCS) is a focal plane instrument for SPICA with imaging and spectroscopic observing capabilities in the mid-infrared wavelength range of 5-38μm. MCS consists of two relay optical modules and following four scientific optical modules of WFC (Wide Field Camera; 5'x 5' field of view, f/11.7 and f/4.2 cameras), LRS (Low Resolution Spectrometer; 2'.5 long slits, prism dispersers, f/5.0 and f/1.7 cameras, spectral resolving power R ? 50-100), MRS (Mid Resolution Spectrometer; echelles, integral field units by image slicer, f/3.3 and f/1.9 cameras, R ? 1100-3000) and HRS (High Resolution Spectrometer; immersed echelles, f/6.0 and f/3.6 cameras, R ? 20000-30000). Here, we present optical design and expected optical performance of MCS. Most parts of MCS optics adopt off-axis reflective system for covering the wide wavelength range of 5-38μm without chromatic aberration and minimizing problems due to changes in shapes and refractive indices of materials from room temperature to cryogenic temperature. In order to achieve the high specification requirements of wide field of view, small F-number and large spectral resolving power with compact size, we employed the paraxial and aberration analysis of off-axial optical systems (Araki 2005 [1]) which is a design method using free-form surfaces for compact reflective optics such as head mount displays. As a result, we have successfully designed compact reflective optics for MCS with as-built performance of diffraction-limited image resolution.
Naoki Isobe, Taiki Kawamuro, Shinki Oyabu, Takao Nakagawa, Shunsuke Baba, Kenichi Yano, Yoshihiro Ueda and Yoshiki Toba : MAXI and AKARI investigation of nearby active galactic nuclei, 7 years of MAXI: monitoring X-ray Transients, 223, 2017.
11.
Itsuki Sakon, Hidehiro Kaneda, Shinki Oyabu, Daisuke Ishihara, Takehiko Wada and Naofumi Fujishiro : Sensitivity estimates for the SPICA Mid-Infrared Instrument (SMI), Space Telescopes and Instrumentation 2016: Optical, Infrared, and Millimeter Wave, Vol.9904, 99043V, 2016.
(要約)
We present the latest results of the sensitivity estimate for spectrometers of the SPICA Mid-Infrared Instrument (SMI). SMI has three spectroscopic channels; low resolution spectrometer (LRS), medium resolution spectrometer (MRS) and high resolution spectrometer (HRS). Taking account of the results of optical design of each spectrometer and the latest information of the expected performance of detector arrays, the continuum sensitivity for a point source, the continuum sensitivity for an extended source, the line sensitivity for a point source, the line sensitivity for an extended source, and the saturation limit are calculated for LRS, MRS and HRS and are provided in this paper.
Tomoko Suzuki, T. Tsutomu Takeuchi, Agnieszka Pollo and Shinki Oyabu : A strong clustering of FIR-selected galaxies in the AKARI All-Sky Survey, Proceedings of the International Astronomical Union, Vol.10, No.S309 (Galaxies in 3D across the Universe), 346-347, 2015.
(要約)
Various previous galaxy surveys have revealed that different types of galaxies show different spatial distributions. By comparing their clustering strengths, we can investigate the relationship between the environments where galaxies reside and the properties of galaxies. This provides us vital information on when, where, and how galaxies are formed. In this study, we focus on FIR-selected galaxies from AKARI All- Sky Survey, which are considered to be dusty star-forming galaxies. We measure their power spectrum and compare our final result with previous studies using different galaxy samples detected at other wavelengths. It is found that there is the very clear wavelength dependence of the clustering strength.
Kohei Ichikawa, Masatoshi Imanishi, Yoshihiro Ueda, Takao Nakagawa, Mai Shirahata, Hidehiro Kaneda and Shinki Oyabu : Unveiling Energy Contribution of Buried AGN in Infrared Galaxies, Suzaku-MAXI 2014: Expanding the Frontiers of the X-ray Universe, 323, 2014.
14.
K. Enya, N. Fujishiro, K. Haze, T. Kotani, H. Kaneda, Shinki Oyabu, D. Ishihara and S. Oseki : A cryogenic dichroic mirror for separating visible light from wideband infrared, Space Telescopes and Instrumentation 2014: Optical, Infrared, and Millimeter Wave, Vol.9143, 91434J, 2014.
(要約)
We present the design, fabrication and test results for a dichroic mirror, which was primarily developed for the SPICA Coronagraph Instrument (SCI), but is potentially useful for various types of astronomical instrument. The dichroic mirror is designed to reflect near- and mid-infrared but to transmit visible light. Two designs, one with 3 layers and one with 5 layers on BK7 glass substrates, are presented. The 3-layer design, consisting of Ag and ZnS, is simpler, and the 5-layer design, consisting of Ag and TiO2 is expected to have better performance. Tape tests, evaluation of the surface figure, and measurements of the reflectivity and transmittance were carried out at ambient temperature in air. The reflectivity obtained from measurements made on mirrors with 5 layers were < 80 % for wavelengths, λ, from 1.2 to 22 μm and < 90 % for λ from 1.8 to 20 μm. The transmittance obtained from measurements made on mirrors with 5 layers were < 70 % for λ between 0.4 and 0.8 μm. Optical ghosting is estimated to be smaller than 10-4 at λ < 1.5 μm. A protective coating for preventing corrosion was applied and its influence on the reflectivity and transmittance evaluated. A study examining the trade-offs imposed by various configurations for obtaining a telescope pointing correction signal was also undertaken.
A. Castro, T. Miyaji, M. Shirahata, Shinki Oyabu, D. Clark, K. Ichikawa, M. Imanishi, T. Nakagawa and Y. Ueda : A 2.5-5 μm spectroscopic study of hard X-ray selected AGNs with AKARI, Multiwavelength AGN Surveys and Studies, Vol.9, No.S304, 66-67, 2014.
(要約)
We explore the relationships between the 3.3 μm polycyclic aromatic hydrocarbon (PAH) feature and active galactic nucleus (AGN) properties of a sample of 54 hard X-ray selected bright AGNs, including both Seyfert 1 and Seyfert 2 type objects, using the InfraRed Camera (IRC) on board the infrared astronomical satellite AKARI. The sample is selected from the 9-month Swift/BAT survey in the 14-195 keV band and all of them have measured X-ray spectra at E <~ 10 keV. These X-ray spectra provide measurements of the neutral hydrogen column density (N H) towards the AGNs. We use the 3.3 μm PAH luminosity (L 3.3μm) as a proxy for star formation activity and hard X-ray luminosity (L 14-195keV) as an indicator of the AGN activity. We searched for possible difference of star-formation activity between type 1 (un-absorbed) and type 2 (absorbed) AGNs. Our regression analysis of log L 14-195keV versus log L 3.3μm shows a positive correlation and the slope seems steeper for type 1/unobscured AGNs than that of type 2/obscured AGNs. The same trend has been found for the log (L 14-195keV/M BH) versus log (L 3.3μm/MBH) correlation. Our analysis show that the circum-nuclear star-formation is more enhanced in type 2/absorbed AGNs than type 1/un-absorbed AGNs for low X-ray luminosity/low Eddington ratio AGNs.
K. Enya, K. Haze, Y. Chibu, T. Kotani, H. Kaneda, Shinki Oyabu, D. Ishihara, S. Oseki, L. Abe and H. Kobayashi : An inverse-polished mirror for wavefront correction of space-based telescopes, Advances in Optical and Mechanical Technologies for Telescopes and Instrumentation, Vol.9151, 91512Y, 2014.
(要約)
In this report we describe our development of a prototype inverse- polished mirror for the passive correction of the static and predictable wavefront errors (WFE) of space-based telescopes, in particular, especially for infrared coronagraphs. An artificial WFE pattern with a root mean square (rms) value of 350 nm was numerically generated to facilitate the design of the prototype mirror. The surface of the mirror is approximately flat, is 50.0 mm in diameter and 15.0 mm thick at the edge. The designed WFE pattern was constructed on the mirror surface by micro-polishing. Both the figure and roughness of the mirror surface were evaluated. The rms value of the measured surface figure was reduced to 135 nm after subtraction of the designed surface figure. The benefit of subtraction to mid-infrared coronagraph performance was simulated, which showed the contrast was improved by a factor of ~100 close to the core (closer than 10 λ/D where λ and D are the wavelength and telescope aperture diameter, respectively) of the coronagraphic image of a point source. An analysis of the power spectrum density shows that the lower frequencies in the WFE are well reproduced on the mirror, while the higher frequencies remain due to the limitations imposed on the controllable spatial resolution by the fabrication process. In this study, inverse-polished mirrors combined with deformable mirrors and their application to ground-based telescopes are also discussed. To fully explore the potential of the inverse-polished mirror, a systematic allocation of the error budget is essential taking into account not only the fabrication accuracy of the mirror but also an evaluation of the telescope and other factors with non-predictable uncertainties.
Yoshiki Toba, Shinki Oyabu, Hideo Matsuhara, A. Matthew Malkan, Daisuke Ishihara, Takehiko Wada, Youichi Ohyama, Satoshi Takita and Chisato Yamauchi : Luminosity and redshift dependence of covering factor of dust torus viewed with AKARI and WISE, Torus Workshop, 2012, 58, 2012.
(要約)
We present the relation between (i) the covering factor (CF) of AGN and mid-infrared (MIR) luminosity and (ii) CF and redshift (0 < z < 0.3) from the 12 and 22 μm luminosity functions (LFs) we made from the Wide-field Infrared Survey Explorer (WISE). Combining the WISE catalog with the Sloan Digital Sky Survey (SDSS) spectroscopic catalog, we selected ?300,000 galaxies at 12 μm and ?30,000 galaxies at 22 μm. We then extracted ?10,000 AGNs at 12 μm and ?5,000 AGNs at 22 μm from them according to the optical emission lines and catalog classification in the SDSS. We found that (i) CF clearly decreases with MIR luminosity, which supports the implications from 18 μm LFs obtained by the Japanese infrared satellite, AKARI, and (ii) CF also seems to decrease with redshift. The latter correlation may result from the close correlation between redshift and luminosity in our magnitude-limited sample, rather than any true cosmic evolution.
18.
Kohei Ichikawa, Yoshihiro Ueda, Yuichi Terashima, Shinki Oyabu, Poshak Gandhi, Keiko Matsuta and Takao Nakagawa : Mid-infrared and hard X-ray luminosity correlation of a complete sample of local AGNs, Torus Workshop, 2012, 109, 2012.
(要約)
We present the mid-infrared (MIR) properties of a complete sample of local active galactic nuclei (AGNs) detected in the Swift/BAT all-sky hard X-ray (14-195 keV) survey, based on the cross matches with the AKARI, IRAS, and WISE infrared all-sky survey catalogs. Out of 135 non- blazar AGNs in the Swift/BAT 9-month catalog, we unambiguously identify the MIR photometric data of 128 sources. We find a good luminosity correlation between the hard X-ray and MIR band over three orders of magnitude (42 ? log LHX ? 45). This suggests that MIR emission is suitable for estimating the AGN intrinsic power. Both X- ray unabsorbed and absorbed AGNs follow the same correlation, implying isotropic infrared emission, as expected in clumpy dust tori rather than homogeneous ones. We also find 9 μm excess sign in the averaged infrared spectral energy distribution of a population of deeply buried ("new type") AGNs. This excess signal could originate from polycyclic aromatic hydrocarbon emission feature, suggesting that their host galaxies have strong starburst activities.
19.
Y. Matsuoka, N. Ienaka, K. Kawara and Shinki Oyabu : New constraints on the cosmic optical background, AIP Conference Proceedings, Vol.1480, No.1, 285, 2012.
(要約)
We present the new constraints on the cosmic optical background (COB) obtained from an analysis of the Pioneer 10/11 Imaging Photopolarimeter (IPP) data. After careful examination of the data quality, the usable measurements free from the zodiacal light are integrated into sky maps at the blue (~0.44 μm) and red (~0.64 μm) bands. Accurate starlight subtraction is achieved by referring to all-sky star catalogs and a Galactic stellar population model down to 32.0 mag. We find that the residual light is separated into two components: one component shows a clear correlation with thermal 100 μm brightness, while another betrays a constant level in the lowest 100 μm brightness region. Presence of the second component is significant after all the uncertainties and possible residual light in the Galaxy are taken into account, thus it most likely has the extragalactic origin (i.e., the COB). The derived COB brightness is 7.9 +/- 4.0 and 7.7 +/- 5.8 nW m-2 sr-1 at the blue and red band, respectively. Based on the comparison with the integrated brightness of galaxies, we conclude that the bulk of the COB is comprised of normal galaxies which have already been resolved by the current deepest observations.
(キーワード)
cosmic background radiation / galaxies / 95.85.Kr / 98.62.Ai / 98.70.Vc / Visible / Origin formation evolution age and star formation / Background radiations
T. Kotani, K. Enya, T. Nakagawa, H. Matsuhara, H. Kataza, M. Kawada, M. Mita, K. Komatsu, H. Uchida, K. Fujiwara, S. Mitani, S. Sakai, K. Haze, H. Kaneda, Shinki Oyabu, D. Ishihara, T. Miyata, S. Sako, T. Nakamura, K. Asano, M. Tamura, J. Nishikawa, T. Yamashita, N. Narita, H. Hayano, S. Oya, E. Kokubo, Y. Itoh, T. Matsuo, M. Fukagawa, H. Shibai, M. Honda, N. Baba, N. Murakami, K. Y. Okamoto, S. Ida, M. Takami, L. Abe, O. Guyon and T. Yamamuro : SPICA coronagraph instrument: characterization of atmospheres and physical parameters of giant planets by direct imaging and spectroscopy, Space Telescopes and Instrumentation 2012: Optical, Infrared, and Millimeter Wave, Vol.8442, 84420F, 2012.
(要約)
We present the current status of the development of the SPICA Coronagraph Instrument (SCI). SPICA is a next-generation 3-meter class infrared telescope, which will be launched in 2022. SCI is high-contrast imaging, spectroscopic instrument mainly for direct detection and spectroscopy of extra-solar planets in the near-to-mid infrared wavelengths to characterize their atmospheres, physical parameters and evolutionary scenarios. SCI is now under the international review process. In this paper, we present a science case of SCI. The main targets of SCI, not only for direct imaging but also for spectroscopy, are young to matured giant planets. We will also show that some of known exoplanets by ground-based direct detection are good targets for SCI, and a number of direct detection planets that are suitable for SCI will be significantly increased in the next decade. Second, a general design of SCI and a key technology including a new high-throughput binary mask coronagraph, will be presented. Furthermore, we will show that SCI is potentially capable of achieving 10-6 contrast by a PSF subtraction method, even with a telescope pointing error. This contrast enhancement will be important to characterize low-mass and cool planets.
Hirokazu Kataza, Takehiko Wada, Itsuki Sakon, Naoto Kobayashi, Yuki Sarugaku, Naofumi Fujishiro, Yuji Ikeda and Shinki Oyabu : Mid-infrared camera and spectrometer on board SPICA, Space Telescopes and Instrumentation 2012: Optical, Infrared, and Millimeter Wave, Vol.8442, 84420Q, 2012.
(要約)
SPICA (Space Infrared Telescope for Cosmology and Astrophysics) is an astronomical mission optimized for mid- and far-infrared astronomy, envisioned for launch in early 2020s. The core wavelength coverage of this mission is 5 to 200 micron. Mid-infrared Camera and Spectrometer (MCS) will provide imaging and spectroscopic observing capabilities in the mid-infrared region with 4 modules. WFC (Wide Field Camera) has two 5 arcminutes square field of view and covers the wavelength range from 5 to 38 micron. MRS (Mid Resolution Spectrometer) has integral field units by image slicer and covers the wavelength range from 12.2 to 37.5 micron simultaneously using dichroic filter and two sets of spectrometers. HRS (High Resolution Spectrometer) covers the wavelength range from 12 to 18 micron with resolving power 20000 to 30000, and it has optional short wavelength channel which covers from 4 to 8 micron with resolving power 30000. LRS (Low Resolution Spectrometer) adopts prism disperser and covers the wavelength range from 5 to 38 micron with resolving power 50 to 100. Here, we present detailed specifications of MCS, optical design, and estimated performance on orbit.
T. Onaka, H. Matsuhara, T. Wada, D. Ishihara, Y. Ohyama, I. Sakon, T. Shimonishi, R. Ohsawa, I. T. Mori, F. Egusa, F. Usui, S. Takita, H. Murakami, Shinki Oyabu, M. Yamagishi, T. Mori, A. Mouri, T. Kondo, S. Suzuki, H. Kaneda, Y. Ita and T. Ootsubo : Summary of observations of the infrared camera (IRC) onboard AKARI, Space Telescopes and Instrumentation 2012: Optical, Infrared, and Millimeter Wave, Vol.8442, 844213, 2012.
(要約)
AKARI, the Japanese satellite mission dedicated to infrared astronomy was launched in 2006 February and exhausted its liquid helium in 2007 August. During the cold mission phase, the Infrared Camera (IRC) onboard carried out an all-sky survey at 9 and 18?m with better spatial resolution and higher sensitivity than IRAS. Both bands also have slightly shorter wavelength coverage than IRAS 12 and 25μm bands and thus provide different information on the infrared sky. All-sky image data of the IRC are now in the final processing and will be released to the public within a year. After the exhaustion of the cryogen, the telescope and focal plane instruments of AKARI had still been kept at sufficiently low temperatures owing to the onboard cryocooler. Near-infrared (NIR) imaging and spectroscopic observations with the IRC had continued until 2011 May, when the spacecraft had a serious problem in the power supply system that forced us to terminate the observation. The IRC carried out nearly 20000 pointing observations in total despite of its near-earth orbit. About a half of them were performed after the exhaustion of the cryogen in the spectroscopic modes, which provided high-sensitivity NIR spectra from 2 to 5?m without disturbance of the terrestrial atmosphere. During the warm mission phase, the temperature of the instrument gradually increased and changed the array operation conditions. We present a summary of AKARI/IRC observations, including the all-sky mid-infrared diffuse data as well as the data taken in the warm mission phase.
Toru Yamada, Ikuru Iwata, Makiko Ando, Mamoru Doi, Tomotsugu Goto, Yuji Ikeda, Masatoshi Imanishi, K. Akio Inoue, Satoru Iwamura, Nobuyuki Kawai, R. Masakazu A. Kobayashi, Tadayuki Kodama, Yutaka Komiyama, Mariko Kubo, Hideo Matsuhara, Ken Mawatari, Yoshiki Matsuoka, Tomoki Morokuma, Hidehiko Nakaya, Koji Ohta, Atsushi Okamoto, Shinki Oyabu, Yohichi Sato, Hiroyuki Sugita, Ryo Tsutsui, Chihiro Tokoku, Jun Toshikawa, Saku Tsuneta, Takehiko Wada, Kiyoto Yabe, Naoki Yasuda and Daisuke Yonetoku : WISH for deep and wide NIR surveys, Space Telescopes and Instrumentation 2012: Optical, Infrared, and Millimeter Wave, Vol.8442, 84421A, 2012.
(要約)
WISH, Wide-field Imaging Surveyor for High-redshiftt, is a space mission concept to conduct very deep and widefield surveys at near infrared wavelength at 1-5μm to study the properties of galaxies at very high redshift beyond the epoch of cosmic reionization. The concept has been developed and studied since 2008 to be proposed for future JAXA/ISAS mission. WISH has a 1.5m-diameter primary mirror and a wide-field imager covering 850 arcmin2. The pixel scale is 0.155 arcsec for 18μm pitch, which properly samples the diffraction-limited image at 1.5μm. The main program is Ultra Deep Survey (UDS) covering 100 deg2 down to 28AB mag at least in five broad bands. We expect to detect <104 galaxies at z=8-9, 103-104 galaxies at z=11-12, and 50-100 galaxies at z<14, many of which can be feasible targets for deep spectroscopy with Extremely Large Telescopes. With recurrent deep observations, detection and light curve monitoring for type-Ia SNe in rest-frame infrared wavelength is also conducted, which is another main science goal of the mission. During the in-orbit 5 years observations, we expect to detect and monitor <2000 type-Ia SNe up to z~2. WISH also conducts Ultra Wide Survey, covering 1000deg2 down to 24-25AB mag as well as Extreme Survey, covering a limited number of fields of view down to 29-30AB mag. We here report the progress of the WISH project including the basic telescope and satellite design as well as the results of the test for a proto- model of the flip-type filter exchanger which works robustly near 100K.
Y. Toba, Shinki Oyabu, H. Matsuhara, D. Ishihara, M. Malkan, T. Wada, H. Kataza, Y. Ohyama and S. Takita : The Mid-Infrared luminosity function of galaxies using the AKARI mid-infrared All-Sky Survey Catalogue, The Spectral Energy Distribution of Galaxies - SED 2011, Vol.7, No.S284, 228-230, 2012.
(要約)
We present the first determination of the 18 μm luminosity function (LF) of galaxies at 0.006 < z < 0.7 (the average redshift is ~ 0.04) using the AKARI mid-infrared All-Sky Survey catalogue. We have selected a 18 μm flux-limited sample of 243 galaxies from the catalogue in the SDSS spectroscopic region. We then classified the sample into four types; Seyfert 1 galaxies (including QSOs), Seyfert 2 galaxies, LINERs and Star-Forming galaxies using mainly [OIII]/Hβ vs. [NII]/Hα line ratios obtained from the SDSS. As a result of constructing Seyfert 1 and Seyfert 2 LFs, we found the following results; (i) the number density ratio of Seyfert 2s to Seyfert 1s is 3.98 +/- 0.41 obtained from Sy1 and Sy2 LFs; this value is larger than the results obtained from optical LFs. (ii) the fraction of Sy2s in the entire AGNs may be anti- correlated with 18 μm luminosity. These results suggest that the torus structure probably depends on the mid-infrared luminosity of AGNs and most of the AGNs in the local Universe are obscured by dust.
(キーワード)
catalogs / surveys / galaxies: active / galaxies: fundamental parameters / galaxies: Seyfert / galaxies: luminosity function / infrared: galaxies
Chris Sedgwick, Stephen Serjeant, Chris Pearson, Shuji Matsuura, Mai Shirahata, Shinki Oyabu, Tomotsugu Goto, Hideo Matsuhara, L. D. Clements, Mattia Negrello, Toshinobu Takagi and J. Glenn White : Far Infrared Luminosity Function of Local Galaxies in the AKARI Deep Field South, The Spectral Energy Distribution of Galaxies - SED 2011, Vol.7, No.S284, 289-291, 2012.
(要約)
We present the first far-infrared luminosity function in the AKARI Deep Field South, a premier deep field of the AKARI Space Telescope, using spectroscopic redshifts obtained with AAOmega. To date, we have found spectroscopic redshifts for 389 galaxies in this field and have measured the local (z<0.25) 90 μm luminosity function using about one-third of these redshifts. The results are in reasonable agreement with recent theoretical predictions.
(キーワード)
galaxies: evolution / galaxies: luminosity function / infrared: galaxies / Astrophysics - Cosmology and Nongalactic Astrophysics
Y. Matsuoka, N. Ienaka, K. Kawara and Shinki Oyabu : Cosmic Optical Background: the view from Pioneer 10/11, The Spectral Energy Distribution of Galaxies - SED 2011, Vol.7, No.S284, 437-441, 2012.
(要約)
We present the new constraints on the cosmic optical background (COB) obtained from an analysis of the Pioneer 10/11 Imaging Photopolarimeter (IPP) data. After careful examination of data quality, the usable measurements free from the zodiacal light are integrated into sky maps at the blue (~0.44 μm) and red (~0.64 μm) bands. Accurate starlight subtraction is achieved by referring to all-sky star catalogs and a Galactic stellar population synthesis model down to 32.0 mag. We find that the residual light is separated into two components: one component shows a clear correlation with thermal 100 μm brightness, while another betrays a constant level in the lowest 100 μm brightness region. Presence of the second component is significant after all the uncertainties and possible residual light in the Galaxy are taken into account, thus it most likely has the extragalactic origin (i.e., the COB). The derived COB brightness is (1.8 +/- 0.9) × 10-9 and (1.2 +/- 0.9) × 10-9 erg s-1 cm-2 sr-1 ?-1 at the blue and red band, respectively, or 7.9 +/- 4.0 and 7.7 +/- 5.8 nW m-2 sr-1. Based on a comparison with the integrated brightness of galaxies, we conclude that the bulk of the COB is comprised of normal galaxies which have already been resolved by the current deepest observations. There seems to be little room for contributions of other populations including ``first stars'' at these wavelengths. On the other hand, the first component of the IPP residual light represents the diffuse Galactic light (DGL)--scattered starlight by the interstellar dust. We derive the mean DGL-to-100 μm brightness ratios of 2.1 × 10-3 and 4.6 × 10-3 at the two bands, which are roughly consistent with the previous observations toward denser dust regions. Extended red emission in the diffuse interstellar medium is also confirmed.
(キーワード)
cosmology: observations - dark matter - diffuse radiation - dust / extinction - galaxies: evolution - infrared: ISM - methods: data analysis - space vehicles
Y. Toba, Shinki Oyabu, H. Matsuhara, M. Malkan, D. Ishihara, T. Wada, S. Takita and C. Yamauchi : Luminosity dependent covering factor of the dust torus around AGN viewed with AKARI and WISE, Proceedings of Science, 34, 2012.
A. Castro, T. Miyaji, T. Nakagawa, M. Shirahata, Shinki Oyabu, M. Imanishi, Y. Ueda and K. Ichikawa : A 2.5-5 micron Spectroscopic Study of Hard X-ray Selected AGNs using AKARI InfraRed Camera, Proceedings of Nuclei of Seyfert galaxies and QSOs - Central engine & conditions of star formation (Seyfert 2012). 6-8 November, 68, 2012.
29.
Shinki Oyabu : Search for Active Galactic Nuclei using AKARI Mid-infrared All-Sky Survey, The Starburst-AGN Connection under the Multiwavelength Limelight, 45, 2011.
(要約)
Many observations have found evidence of the presence of a large number of heavily obscured active galactic nuclei (AGNs). These AGNs contribute to the local black hole mass density, and are potentially important contributors to the growth of supermassive black holes throughout the history of the universe. However, the nature of this population, even in the local universe, is only poorly understood, because of the strong selection bias against finding them at optical wavelengths. Mid-infrared AGN searches can overcome this obstacle by penetrating through dust extinction to identify most of the AGN population, including Type 2 Seyferts and buried AGNs. Using AKARI Mid-infrared All-Sky Survey and the follow-up observations, we are performing AGN search as well as the study of AGN natures. We will present our discovery of two obscured AGNs that do not show any AGN features in other bands. In addition, we will present new mid-infrared luminosity functions of AGNs.
30.
S. Takita, N. Ikeda, I. Yamamura, Shinki Oyabu, Y. Kitamura and D. Ishihara : Development of AKARI Reduction Tools for IRC Slow-Scan, Astronomical Data Analysis Software and Systems XIX, Vol.434, 429, 2010.
(要約)
We are developing the AKARI reduction tools for the IRC slow-scan. To create an image, we need position information provided from the satellite telemetry. However, the typical accuracy of the position is as large as ?10". Here, we developed a software called self-pointing reconstruction, which is the most important part of the tools. Using this method, the position accuracy reaches as good as ?1".
31.
Shinki Oyabu, Y. Toba, D. Ishihara, H. Matsuhara, T. Wada, Y. Oyama and M. Malkan : Search for Active Galactic Nuclei using AKARI Mid-infrared All-Sky Survey, The First Year of MAXI: Monitoring Variable X-ray Sources, 46, 2010.
(要約)
AKARI, the Japanese infrared satellite launched at February 2006, have a primary mirror of 70cm diameter cooled with the combination of liquid helium and mechanical coolers. It had unique capabilities of near- infrared spectroscopy in the wavelength between 2um and 5um, all-sky survey in the mid- and far-infrared as well as broadband filters consecutively covering the near-, mid- and far-infrared wavelengths. Using the point source catalog in the AKARI Mid-infrared All-Sky Survey, we are searching for Active Galactic Nuclei (AGNs), not only normal AGNs but also dusty AGNs, in the local Universe. AKARI provides remarkable improvement in sensitivity and spatial resolution upon the previous all- sky survey with IRAS. We are performing the follow-up observations of mid-infrared sources showing red-color in the near- and mid-infrared bands with the AKARI near-infrared spectroscopy and the ground-based optical spectroscopy. During the follow-up observations, we have started to detect hidden AGNs located in galaxies that were previously unrecognized to contain an AGN at other wavelengths.
32.
Y. Toba, Shinki Oyabu, D. Ishihara, H. Matsuhara, T. Wada, Y. Ohyama and M. Malkan : The optical spectrum classifications of mid-infrared excess sources found by the AKARI All-SKy Survey, The First Year of MAXI: Monitoring Variable X-ray Sources, 48, 2010.
(要約)
We present optical spectrum classifications of mid-infrared excess sources found by the AKARI All-Sky Survey. AKARI is the first infrared astronomical satellite in Japan launched in 2006. AKARI's main purpose is mid-infrared (9 and 18 micron) All-Sky survey as well as far-infrared (65, 90, 140 and 160 micron) All-Sky Survey. The spatial resolutions and sensitivities are one-order better than those of Infrared Astronomical Satellite IRAS which performed previous All-Sky Survey. As a result, AKARI can detect much fainter objects in much higher pointing accuracy. We are searching for Active Galactic Nuclei (AGNs) using AKARI mid- infrared All-Sky Survey catalog. One of the advantages of the mid- infrared searches is that we can directly detect infrared radiation from the dust torus which surrounds the central engine. About 2000 AGN candidates are selected by comparing their 9um fluxes with Ks-band photometry of Two Micron All-Sky Survey. Then, we obtained 130 spectra from our optical spectroscopic observations at Kitt Peak National Observatory and Lick Observatory and the archived data in the Sloan Digital Sky Survey (SDSS). We have classified these spectra into several types (type I AGNs, type II AGNs, Star-Forming galaxies etc) by these optical emission line ratios.
AKARI, the Japanese satellite mission dedicated for infrared astronomy launched in 2006 February, exhausted its 180 litter liquid helium (LHe) in 2007 August. After the LHe exhaustion, the telescope and focal plane of AKARI have still been kept less than 50K by the onboard cryocooler and near-infrared (NIR) observations with the Infrared Camera (IRC) are continuing. The data reduction software optimized for the warm mission enables us to carry out efficient and sensitive observations in the NIR despite the increase of hot pixels. In particular, the NIR spectroscopic capability of the IRC provides a unique opportunity to obtain spectra in 2.5-5μm with a high sensitivity, which will not be able to be carried out with any other facilities until JWST. An overview of the AKARI warm mission is given together with the performance and some observational results taken during the warm mission.
Toru Yamada, Mamoru Doi, Tomotsugu Goto, Yuji Ikeda, Masatoshi Imanishi, Akio Inoue, Satoru Iwamura, Ikuru Iwata, Nobuyuki Kawai, R. Masakazu A. Kobayashi, Tadayuki Kodama, Yutaka Komiyama, Hideo Matsuhara, Yoshiki Matsuoka, Tomoki Morokuma, Kouji Ohta, Shinki Oyabu, Yoichi Sato, Hiroyuki Sugita, Ryo Tsutsui, Chihiro Tokoku, Saku Tsuneta, Takehiko Wada, Kiyoto Yabe, Naoki Yasuda and Daisuke Yonetoku : WISH: wide-field imaging surveyor at high redshift, Space Telescopes and Instrumentation 2010: Optical, Infrared, and Millimeter Wave, Vol.7731, 77311Q, 2010.
(要約)
WISH is a new space science mission concept whose primary goal is to study the first galaxies in the early universe. We will launch a 1.5m telescope equipped with 1000 arcmin2 wide-field NIR camera by late 2010's in order to conduct unique ultra-deep and wide-area sky surveys at 1-5 micron. The primary science goal of WISH mission is pushing the high-redshift frontier beyond the epoch of reionization by utilizing its unique imaging capability and the dedicated survey strategy. We expect to detect ~104 galaxies at z=8-9, ~3-6x103 galaxies at z=11-12, and ~50-100 galaxies at z=14-17 within about 5 years of the planned mission life time. It is worth mentioning that a large fraction of these objects may be bright enough for the spectroscopic observations with the extremely large telescopes. By adopting the optimized strategy for the recurrent observations to reach the depth, we also use the surveys to detect transient objects. Type Ia Supernova cosmology is thus another important primary goal of WISH. A unique optical layout has been developed to achieve the diffraction- limited imaging at 1-5micron over the required large area. Cooling the mirror and telescope to ~100K is needed to achieve the zodiacal light limited imaging and WISH will achieve the required temperature by passive cooling in the stable thermal environment at the orbit near Sun- Earth L2. We are conducting the conceptual studies and development for the important components of WISH including the exchange mechanism for the wide-field filters as well as the primary mirror fixation.
T. Takagi, Y. Ohyama, H. Matsuhara, T. Wada, Shinki Oyabu, T. Goto, H. Hanami, P. C. Pearson, S. Serjeant, M. Negrello, J. G. White, M. H. Lee, M. Im and M. Malkan : The AKARI Extragalactic Large Area Survey Towards the North Ecliptic Pole, AIP Conference Proceedings, Vol.1240, No.1, 47, 2010.
(要約)
Large area surveys in the infrared wavelengths have revealed a significant evolution of the star formation activity of the universe in the past. Extragalactic surveys we have conduced with AKARI towards the north ecliptic pole (NEP) are unique, in terms of a comprehensive wavelength coverage from 2 to 24 μm using all 9 photometric bands of the IRC. This includes new wavelength windows for extragalactic surveys, such as 18 μm. We demonstrate that this IRC all-band photometry is capable of tracing a steep rise in the flux at the blue side of the polycyclic aromatic hydrocarbon (PAH) 6.2 μm emission feature of infrared luminous galaxies at z<1. Starburst-dominated ULIRGs are identified using IRC all-band photometry. The PAH-to-total IR luminosity ratio of these starburst ULIRGs is systematically higher than that of local ULIRGs. The nature of ULIRGs could be different from local ones even at z~1.
(キーワード)
star formation / infrared sources (astronomical) / photometry / red shift / astronomical spectra / 97.10.Bt / 98.70.Lt / 95.55.Qf / 98.62.Py / 95.75.Fg / Star formation / IR sources / Photometric polarimetric and spectroscopic instrumentation / Distances redshifts radial velocities / spatial distribution of galaxies / Spectroscopy and spectrophotometry
Shinki Oyabu : AKARI Infrared Views of AGNs, Co-Evolution of Central Black Holes and Galaxies, Vol.5, No.S267, 129, 2010.
(要約)
The Japanese infrared satellite AKARI has unique capabilities for near- infrared spectroscopy and an all-sky survey in the mid- and far- infrared. We present the recent results on active galactic nuclei that use the unique capabilities of AKARI.
(キーワード)
galaxies: active / infrared: galaxies / quasars: emission lines
Shinki Oyabu, K. Kawara, Y. Tsuzuki, Y. Matsuoka, H. Sameshima, N. Asami and Y. Ohyama : AKARI Near and Mid-Infrared Spectroscopy of APM 08279+5255 at z=3.91, AKARI, a Light to Illuminate the Misty Universe, Vol.418, 233, 2009.
(要約)
We present rest-frame optical/near-infrared spectra of the gravitationally lensed quasar APM 08279+5255 at z=3.91 that has been taken using the Infrared Camera (IRC) onboard the AKARI infrared satellite. The observed continuum consists of two components; a power- law component dominating optical wavelengths which is the direct light from the central source and thermal emission dominating near-infrared wavelengths which is attributed to the emission from hot dust in the circumnuclear region. The thermal emission well represents optically thick emission by hot dust at T ? 1300 K with &tau2μm > 2. Thus, our observations directly detected the optically thick region of hot dust in APM 08279+5255. HI recombination lines of Hα(0.656 μm), Paα(1.875 μm), and Paβ(1.282 μm) are clearly detected at 3.2, 6.3, and 9.3 μm. Simulations with the photoionization models suggest that APM 08279+5255 has BLR(Broad Line Region) clouds characterized by log nH ? 12 - 14 for the gas density, log U ? -2 - -6 for the ionization parameter, and E(B-V)? 0.3 - 0.6 for the broad line region. Thus, optically thick emission of hot dust support an idea on non- spherical distribution of dust near the central source, consistent with the Active Galactic Nuclei model with the dust torus.
38.
M. H. Lee, J. S. Kim, M. Im, G. M. Lee, T. Wada, H. Matsuhara, Shinki Oyabu and Nep Survey Team : Galactic and Extragalactic Sources in the North Ecliptic Pole: Wide Field Survey, AKARI, a Light to Illuminate the Misty Universe, Vol.418, 291, 2009.
(要約)
The North Ecliptic Pole (NEP) Wide Survey was carried out for about one year starting from May 2006 with 9 passbands from 2.5 to 24 μm and the areal coverage of about 5.8 sq. degrees centered on NEP. We present the initial results of the data analysis of all passbands except for the 24 μm. The survey depth reaches to around 22 magnitude (AB) at the near infrared (NIR) bands, and ? 18.5 magnitude at the mid infrared (MIR) bands such as 15 and 18 μm. We matched our infrared sources with the optical sources detected in CFHT imaging survey of about 2 sq. degree area that lies inside the NEP-Wide survey region in order to characterize the nature of infrared sources. The stars are identified by the stellarity parameter of CFHT's r'-band image data given by SExtractor. The fraction of the stars among the infrared sources are found to dependent sensitively on the brightness as well as the wavelength. For example, the majority of bright sources in 9 and 11 μm are stars while stellar fraction decreases toward fainter sources. The stellar fraction at longer 15 and 18 μm bands remains to be less than 10% regardless of the brightness. Most of the non-stellar objects detected in mid-infrared are found to be star forming disk galaxies, with smaller fraction of early type galaxies and AGNs.
39.
H. Matsuhara, T. Wada, Shinki Oyabu, T. Takagi, P. C. Pearson, A. M. Malkan, J. G. White, M. Negrello, S. Serjeant, Y. Ohyama, T. Goto, M. Im, M. H. Lee, G. M. Lee, K. Imai, H. Hanami, T. Ishigaki, K. Wada and T. Nakagawa : Extremely Red Mid-infrared Selected Objects in the AKARI NEP Deep Field: Dust Obscured Type-1 AGN?, AKARI, a Light to Illuminate the Misty Universe, Vol.418, 515, 2009.
(要約)
We describe observational characteristics of three Extremely Red MIR- bright Objects (ERMOs, satisfying R - [15] ? 6.5 AB mag) found in the AKARI North Ecliptic Pole (NEP) deep field at z=1.5-2.2, showing broad Mg II emission (?5000 km sec-1) while their broad-band spectral energy distributions (SEDs) at optical and mid-infrared are power-law, similar to that of the type-2 AGN. Since their SEDs cannot be explained solely by any AGN dust torus templates, we propose that the stellar population co-exists with the AGN dust torus. The interstellar dust clouds associated with the stellar population may be responsible for the extinction of the broad-line regions.
40.
J. H. Seo, T. Matsumoto, M. H. Lee, T. Wada, S. Matsuura, Shinki Oyabu and H. Matsuhara : On the Removal of Point and Extended Sources from NIR Image Data of the AKARI's NEP Monitor Field, AKARI, a Light to Illuminate the Misty Universe, Vol.418, 539, 2009.
(要約)
The imaging data resulting from deep sky observations contain the diffuse component coming from the foreground medium and from unresolved faint objects. AKARI has made very deep imaging observations of a `Monitor Field' near the North Ecliptic Pole (NEP) to check the stability of the instruments. We have created diffuse maps from this data by removing the contributions from known point and extended sources, by applying a 2ς clipping method to remove the bright resolved objects. However, we find excess signals around the rims of the clipped regions that are believed to be due to contributions by the outer parts of the point spread function (PSF), which could then be further removed by careful modeling of the PSF. We have further modeled the extended objects using high resolution near infrared images taken by large aperture ground based telescopes. From this technique, we have generated NIR images of extended sources by convolving a high resolution IR image with the NIR PSF of AKARI, and obtained diffuse images which can be used to study the foreground and background emission.
41.
M. Shirahata, S. Matsuura, H. Matsuhara, T. Takagi, Shinki Oyabu, T. Wada, T. Nakagawa, M. Kawada, T. T. Takeuchi, B. Hatsukade, K. Kohno, P. C. Pearson, S. Serjeant and G. White : SPICA Deep Cosmological Survey: From AKARI to SPICA, The Next-Generation Infrared Space Mission: SPICA, 04012, 2009.
(要約)
On the basis of the results of the AKARI far-infrared deep surveys, we propose a multi-wavelength far-infrared deep cosmological survey with SAFARI on SPICA. We have carried out a far-infrared deep cosmological survey with AKARI, and successfully obtained the galaxy counts and new limits on the absolute brightness of the cosmic far-infrared background. These results provide strong constraints on evolutionary scenarios, and suggest the necessity for a new model to explain galaxy evolution. Thanks to the excellent sensitivity and spatial resolution of SPICA/SAFARI, we will be able to resolve the cosmic infrared background into individual objects with 3 times or more higher spatial resolution than that of AKARI, and will also be able to conduct infrared photometry and spectroscopy on those objects. The far-infrared deep survey with SPICA/SAFARI will be an ideal opportunity to reveal the origin of the cosmic far-infrared background residual brightness and fluctuations. These observation will allow us to reveal the star formation history in the early Universe without the uncertainty of dust attenuation, which is essential if we are to understand the process of galaxy formation.
D. Ishihara, T. Onaka, H. Kataza, H. Fujiwara, S. Takita, C. Alfageme, M. Cohen, N. Fujishiro, P. Garcia-Lario, S. Hasegawa, Y. Ita, W. Kim, T. Nakagawa, H. Matsuhara, T. Matsumoto, H. Murakami, Y. Ohyama, Shinki Oyabu, J. Pyo, I. Sakon, A. Salama, C. Stephenson, H. Shibai, T. Tanabe, K. Uemizu, M. Ueno, F. Usui, T. Wada, H. Watarai, C. Yamauchi and I. Yamamura : AKARI Mid-Infrared All-sky Survey, AIP Conference Proceedings, Vol.1158, 127, 2009.
(要約)
AKARI All-sky Survey observations were carried out in the mid- to far- infrared spectral region with six photometric bands during the cryogenic mission phase of AKARI from May 8, 2006 to August 26, 2007. This paper reports the mid-infrared part of the AKARI all-sky survey. It was carried out with two mid-infrared broad bands centered at 9 and 18 μm. More than 90 percent of entire sky was observed by both bands during this period. The 5ς sensitivities for point sources are about 50 and 120 mJy, respectively. The spatial resolution is better than 10'' at both bands. The AKARI mid-infrared survey achieved a deeper sensitivity and a finer spatial resolution than the previous IRAS survey, the AKARI mid- infrared survey has the sensitivity to detect a debris disk of β Pic at a distance of 100 pc and several new debris disk candidates have already been discovered at 18 μm in a preliminary study, separately discussed by Fujiwara et al. (in this volume). More debris disk candidates are expected to be found in further investigations, which will make a significant impact on the statistical study of debris disks.
(キーワード)
95.80.+p / 95.75.Fg / 97.10.Bt / Astronomical catalogs atlases sky surveys databases retrieval systems archives etc. / Spectroscopy and spectrophotometry / Star formation
T. Takagi, H. Matsuhara, S. Matsuura, T. Wada, Shinki Oyabu, H. Hanami, T. Goto, Y. Ohyama, M. Shirahata, P. C. Pearson, M. H. Lee, M. Im, S. Serjeant, G. White and T. Nakagawa : The AKARI Cosmological Surveys: Initial Results and New Capabilities, Panoramic Views of Galaxy Formation and Evolution, Vol.399, 268, 2008.
(要約)
Using AKARI, the first Japanese satellite dedicated to infrared astronomy, we conducted multi-band large-area surveys around the ecliptic poles. The north ecliptic pole (NEP) is the best region for AKARI which has a sun-synchronous orbit that allows it conduct legacy surveys with all AKARI bands, i.e. nine bands in 2 -- 24 μm and 4 bands in 65 -- 160 μm. We prove that this survey, which has such unprecedented infrared wavelength coverage, is certainly unique and useful to search out new galaxy populations such as "PAH-luminous" galaxies.
44.
Shinki Oyabu, H. Matsuhara, T. Wada, T. Takagi, H. Hanami, Y. Ohyama, T. Goto, P. C. Pearson, M. H. Lee, M. Im, S. Serjeant, G. White and T. Nakagawa : The AKARI North Ecliptic Pole Surveys, Panoramic Views of Galaxy Formation and Evolution, Vol.399, 286, 2008.
(要約)
We present the North Ecliptic Pole (NEP) Surveys with Infrared Camera (IRC) onboard the AKARI infrared satellite. Two NEP surveys were designed: NEP-Deep was deep and NEP-Wide was wide, but shallow. One of the unique characteristics of IRC is nine broad-band filters which cover the continuous wavelength from 2 to 26 μm and all IRC filters were used for both surveys. We also present the status of multi-wavelength follow- up.
45.
Daisuke Ishihara, Takashi Onaka, Hirokazu Kataza, Hideaki Fujiwara, Satoshi Takita, Carlos Alfageme, Martin Cohen, Naofumi Fujishiro, Pedro Garcia-Lario, Sunao Hasegawa, Yoshifusa Ita, Woojung Kim, Takao Nakagawa, Hideo Matsuhara, Toshio Matsumoto, Hiroshi Murakami, Youichi Ohyama, Shinki Oyabu, Jeonghyun Pyo, Itsuki Sakon, Alberto Salama, Craig Stephenson, Hiroshi Shibai, Toshihiko Tanabe, Kazunori Uemizu, Munetaka Ueno, Fumihiko Usui, Takehiko Wada, Hidenori Watarai, Chisato Yamauchi and Issei Yamamura : Mid-infrared all-sky survey with AKARI/IRC, Space Telescopes and Instrumentation 2008: Optical, Infrared, and Millimeter, Vol.7010, 70100B, 2008.
(要約)
AKARI is the first Japanese astronomical infrared satellite mission orbiting around the Earth in a sun-synchronous polar orbit at the altitude of 700 km. One of the major observation programs of the AKARI is an all-sky survey in the mid- to far-infrared spectral regions with 6 photometric bands. The mid-infrared part of the AKARI All-Sky Survey was carried out with the Infrared Camera (IRC) at the 9 and 18 ??m bands with the sensitivity of about 50 and 120 mJy (5ς per scan), respectively. The spatial resolution is about 9.4" at both bands. AKARI mid-infrared (MIR) all-sky survey substantially improves the MIR dataset of the IRAS survey of two decades ago and provides a significant database for studies of various fields of astronomy ranging from star- formation and debris disk systems to cosmology. This paper describes the current status of the data reduction and the characteristics of the AKARI MIR all-sky survey data.
Itsuki Sakon, Takashi Onaka, Takehiko Wada, Youichi Ohyama, Hideo Matsuhara, Naofumi Fujishiro, Daisuke Ishihara, Yoshifusa Ita, Hidehiro Kaneda, Hirokazu Kataza, Woojung Kim, Toshio Matsumoto, Hiroshi Murakami, Takao Nakagawa, Shinki Oyabu, Toshihiko Tanabe, Toshinobu Takagi, Kazunori Uemizu, Munetaka Ueno, Fumihiko Usui, Hidenori Watarai and Martin Cohen : Data reduction techniques for slit and slit-less spectroscopy of diffuse emission with the Infrared Camera onboard AKARI, Space Telescopes and Instrumentation 2008: Optical, Infrared, and Millimeter, Vol.7010, 70102Y, 2008.
(要約)
Infrared Camera (IRC) onboard AKARI satellite has carried out more than 4000 pointed observations during the phases 1 and 2, a significant amount of which were performed in the spectroscopic mode. In this paper, we investigate the properties of the spectroscopic data taken with MIR-S channel and propose a new data reduction procedure for slit-less spectroscopy of sources embedded in complicated diffuse background structures. The relative strengths of the 0th to 1st order light as well as the efficiency profiles of the 2nd order light are examined for various objects taken with MIR-S dispersers. The boundary shapes of the aperture mask are determined by using the spectroscopic data of uniform zodiacal emission. Based on these results, if the appropriate template spectra of zodiacal light emission and the diffuse background emission are prepared and the geometries of the diffuse structures are obtained by the imaging data, we can reproduce the slit-less spectroscopic patterns made by a uniform zodiacal emission and the diffuse background emission by a convolution of those template profiles. This technique enables us to obtain the spectra of infrared sources in highly complicated diffuse background and/or foreground structures, such as in the Galactic plane and in nearby galaxies.
Takehiko Wada, Takashi Onaka, Hideo Matsuhara, Naofumi Fujishiro, Hideaki Fujiwara, Daisuke Ishihara, Yoshifusa Ita, Hirokazu Kataza, Woojung Kim, Toshio Matsumoto, Hiroshi Murakami, Youichi Ohyama, Shinki Oyabu, Itsuki Sakon, Toshihiko Tanabé, Tsutomu Tange, Toshinobu Takagi, Satoshi Takita, Kazunori Uemizu, Munetaka Ueno, Fumihiko Usui, Hidenori Watarai, Martin Cohen, Keigo Enya, Takafumi Ootsubo, P. Chris Pearson, Norihide Takeyama, Tomoyasu Yamamuro and Yuji Ikeda : The Infrared Camera (IRC) for AKARI: in-flight imaging performance and the post cryogen mission, Space Telescopes and Instrumentation 2008: Optical, Infrared, and Millimeter, Vol.7010, 70100C, 2008.
(要約)
The Infrared Camera (IRC) is one of two focal-plane instruments on the AKARI satellite. It is designed for wide-field deep imaging and low- resolution spectroscopy in the near- to mid-infrared (1.8-26.5 micron) in the pointed observation mode of AKARI. The IRC is also operated in the survey mode to make an All-Sky Survey at 9 and 18 microns. The IRC is composed of three channels. The NIR channel (1.8-5.5 micron) employs a 512x412 InSb photodiode array, whereas both the MIR-S (4.6-13.4 micron) and MIR-L (12.6-26.5 micron) channels use 256x256 Si:As impurity band conduction (IBC) arrays. Each of the three channels has a field- ofview of approximately 10x10 arcmin., and they are operated simultaneously. The NIR and MIR-S channels share the same field-of-view by virtue of a beam splitter. The MIR-L observes the sky about 25 arcmin. away from the NIR/MIR-S field-of-view. The in-flight performance of the IRC has been confirmed to be in agreement with the pre-flight expectation. More than 4000 pointed observations dedicated for the IRC are successfully completed, and more than 90% of the sky are covered by the all-sky survey before the exhaustion of the Akari's cryogen. The focal-plane instruments are currently cooled by the mechanical cooler and only the NIR channel is still working properly. Brief introduction, in-flight performance and scientific highlights from the IRC cool mission, together with the result of performance test in the warm mission, are presented.
Y. Ohyama, T. Wada, T. Takagi, T. Nakagawa, H. Matsuhara, S. Matsuura, C. Pearson, Shinki Oyabu, D. Ishihara, W. Kim, N. Fujishiro, M. Shirahata, K. Watanabe, M. Kawada, N. Murakami, Y. Taniguchi, M. Imanishi, T. T. Takeuchi and I. Sakon : The Slit-Less Spectroscopic Survey of Galaxies (SPICY) with the InfraRed Camera (IRC) Onboard AKARI (ASTRO-F) Satellite, Infrared Diagnostics of Galaxy Evolution, Vol.381, 517, 2008.
(要約)
AKARI (formerly ASTRO-F) is a new space telescope for NIR-MIR-FIR observations. The InfraRed Camera (IRC) onboard, covering NIR-MIR, has a capability of low-resolution (R=λ/?λ=20-50) slit-less spectroscopy, and one can simultaneously obtain spectral information of all objects within the camera's large FOV (10× 10 arcmin^2) over wide wavelength range (2-26μm). To exploit this unique capability, we will perform a deep NIR- MIR spectroscopic survey, the `S'pectrosco`PIC' surve`Y' of galaxies (the `SPICY' mission program), down to ? 1 mJy around 15-24μm, to study galaxy evolution at z? 0.5-1.0.
49.
Y. Ohyama, T. Wada, I. Sakon, M. Ishigaki, T. Onaka and Shinki Oyabu : Serendipitous Spectroscopic Detection of Faint Galaxies at MIR with the IRC Onboard the AKARI During Its In-orbit PV Period, Galaxy Evolution across the Hubble Time, Vol.2, No.S235, 325, 2007.
(要約)
The AKARI (formally ASTRO-F) is a space telescope for near-mid-far infrared observations launched on February 2006. One of the two focal- plane instruments, the InfraRed Camera (IRC), is composed of three individual wide-field cameras to cover near-mid infrared wavelength, and each camera is equipped with a selectable filter wheel mounting two transmitting dispersers (grisms and prism) for spectroscopy. With this instrument, slit-less spectroscopy can be performed, i.e., one can simultaneously obtain spectral information of all objects within the camera's field of view (about 10x10 arcmin2) over wide wavelength range (2-26μm), without any a priori source information. With these unique capabilities, we expect to obtain excellent sample of galaxies for studying their evolution. Specifically, we may be able to investigate I) What contributes to the excess found in mid-infrared source count studies with ISO/ Spitzer surveys? How does the luminosity function evolve with redshift? II) How do the spectral features (PAH, etc.) evolve with redshift? How do PAH, mid-infrared, and far-infrared luminosities correlate with each other? We have performed some IRC spectroscopic observations during its in-orbit performance verification period, and in this paper we show examples of IRC spectra of faint galaxies obtained during this period. Although we have taken only a very small number of frames for initial flux and wavelength calibrations, etc., we have serendipitously detected some faint galaxies that are as faint as a few - several mJy in flux. In spite of their faintness, they can be easily recognized by their prominent spectroscopic features (e.g., PAH emission lines), and we can investigate their basic properties, such as redshift and types of activity, by directly analyzing their spectra. We believe that initial success of searching faint galaxies spectroscopically at mid-infrared clearly indicates the power of mid-infrared slit-less spectroscopy as a tool of studying galaxy evolution.
H. Matsuhara, H. Murakami, T. Nakagawa, T. Wada, S. Matsuura, Shinki Oyabu, T. Takagi, P. C. Pearson, H. Kaneda, F. Usui, M. Shirahata, H. Shibai, M. Kawada, T. Onaka and Y. Doi : AKARI in Orbit-Scientific Potential for Understanding Galaxy Evolution, Galaxy Evolution across the Hubble Time, Vol.235, 322, 2007.
(要約)
The AKARI (formerly known as ASTRO-F) mission is the first Japanese satellite dedicated for large area surveys in the infrared. AKARI was launched successfully on February 22nd 2006 (JST) from JAXA's Uchinoura Space Centre, Japan. AKARI is now orbiting around the Earth in a Sun- synchronous polar orbit at the altitude of 700km. The 68.5cm aperture telescope and scientific instruments are cooled to 6K by liquid Helium and mechanical coolers. The expected liquid Helium holding time is about one year after the successful aperture lid-opening on 2006 April 13th (JST). AKARI will perform the most advanced all-sky survey in 6 mid- to far-infrared wavebands since the preceding IRAS mission over 2 decades ago. Deep imaging and spectroscopic surveys with pointed observations are also on-going in 13 wavelength bands from 2-160micron. AKARI is a perfect complement to Spitzer in respect of its wide sky area and wavelength coverage. In this poster we present the unique characteristics of AKARI and its scientific potential for understanding of galaxy evolution. Not only the All-Sky Survey but also the deep pointing surveys near the ecliptic poles over ?15 square degrees will be particularly well suited to construct the luminosity functions of the infrared galaxies, to evaluate their clustering nature, and also to discover rare, exotic objects at various redshifts out to z ? 3. AKARI is also capable of detecting and measuring the spectrum and the fluctuations of the cosmic infrared background. We have confirmed that the in-orbit sensitivity and spatial resolution of the all-sky survey and the pointing surveys are sufficient to obtain the scientific goals listed above.
D. Ishihara, T. Onaka, H. Kataza, T. Wada, H. Matsuhara, M. Ueno, N. Fujishiro, W. Kim, K. Uemizu, Y. Ohyama, Shinki Oyabu, Y. Ita, I. Sakon, H. Fujiwara, S. Hasegawa, T. Matsumoto, I. Yamamura, T. Tanab?, H. Murakami, H. Watarai and M. Cohen : Mid-infrared all-sky survey with AKARI., Memorie della Societa Astronomica Italiana, Vol.77, 1089, 2006.
(要約)
AKARI (formerly called ASTRO-F) is the first Japanese astronomical infrared satellite and it is now in a sun-synchronous polar orbit at the altitude of 700 km. One of the major programs of AKARI observations is an all-sky survey in the mid- to far-infrared spectral region with 6 photometric bands. AKARI has a 685mm telescope, which is cooled down to about 6K by superfluid liquid helium and mechanical coolers. The expected liquid helium holding time is longer than one year. The AKARI mid-infrared (MIR) survey is being carried out with the 9 and 18 mu m bands and the 5sigma sensitivities are estimated to be better than 80 and 130 mJy, respectively. The spatial resolution is better than 10 arcseconds at both bands. The sensitivity and spatial resolution of the MIR survey have been verified in orbit. The AKARI MIR survey will achieve a deeper sensitivity and a finer spatial resolution by about an order of magnitude than the previous survey of the 12 and 25 mu m with IRAS. It will provide a unique and significant database for studies of various fields of astronomy, ranging from star-formation and debris disk systems to cosmology. The first AKARI point source catalogue is planned to be released to the public 2 years after the completion of the survey. This paper reports the flight performance and the current status of the AKARI MIR survey.
(キーワード)
Surveys / Infrared: general / Galaxy: general / ISM: general
52.
T. Sakurai, K. Dobashi, M. Kaiden, S. Nishiura, S. Takano, K. Kawara, Shinki Oyabu, T. Kozasa and K. Fukuhara : Molecular Cloud Core MCLD 123.5+24.9 in Polaris Cirrus, Protostars and Planets V Posters, 8138, 2005.
Institute of Astronomy, University of Tokyo is now planning to build a 6.5-m optical-infrared telescope in Atacama, Chile. This project is called "Univ. Tokyo Atacama Observatory (TAO)", and the site evaluation is now under way. As a part of this evaluation process, we started an investigation to compare the astronomical seeing at Atacama with that at Mauna Kea. Here, we report preliminary results of seeing measurements at several sites in Atacama, carried out on October 2003. In order to separate the temporal and site-to-site variation of the seeing, we used two sets of Differential Image Motion Monitors (DIMMs), each of which has two pairs of 7.4 cm sub-apertures with 20.5 cm separation. Three sites were investigated; the point near the TAO weather station (4,950m), the summit of Cello Chico (5,150m) and the point at 5,430m altitude on Cello Toco. Simultaneous measurements were carried out for three half nights out of four half nights measurements. Although the amount of our data is very limited, the results suggest following: 1) Seeing becomes better and more stable as time passing to midnight (eg. From 0."7 to 0."4 at V-band). 2) Higher altitude sites show better seeing than lower altitude sites.
Yuko Kakazu, Takashi Murayama, Yoshiaki Taniguchi, B. D. Sanders, S. Veilleux, S. Min Yun, Shinki Oyabu, Kimiaki Kawara, Haruyuki Okuda, Toshio Matsumoto, Ken-Ichi Wakamatsu, Yoshiaki Sofue, Hideo Matsuhara, Yasunori Sato, D. R. Joseph and L. L. Cowie : Optical Identification of the ISOPHOTFIR Sources, Studies of Galaxies in the Young Universe with New Generation Telescope, 129-132, 2004.
(要約)
We present the optical follow up observations of the ISOPHOTFIR sources found in our 175 micron deep survey in the Lockman Hole using ISOPHOT on board ISO (Kawara et al. 1998, AA, 328, L9). Optical and NIR observations were made using ESI and NIRSPEC on the Keck II, IRCS on the Subaru, the 8k mosaic CCD camera on the UH88, and VLA. We have identified optical counterparts of 35 ISOPHOT FIR sources with redshift between 0.03 and 1.6. We discuss their observational properties.
55.
E. Verner, F. Bruhwheiler, Y. Tsuzuki, K. Kawara, Y. Yoshii and Shinki Oyabu : Fe+ Emission in PG1626+554: Model Predictions and HST/FOS Observations, American Astronomical Society Meeting Abstracts, Vol.203, 78.15, 2003.
(要約)
Recently, the number of observational efforts to measure the Fe II /Mg II emission ratios in QSOs has increased, due to their potential to give a clue to understanding of host galaxies and star formation in quasars. In our first attempt to translate these observational measurements into abundances, we use numerical simulations of Fe II ion and spectra of quasar, PG 1626+554, obtained with the HST/FOS. The Fe II emission contributes to the Mg II doublet which complicates measurement of Fe II(UV)/Mg II emission ratio. We discuss the observational errors in UV and optical parts of PG 1626+554 spectra that affect Fe II flux measurements. Then we demonstrate how to use Fe II (UV) band, Fe II (optical) band and Mg II (UV) doublet fluxes to derive the iron abundance. We utilize the most sophisticated Fe II ion model (830 levels) to obtain the best fit with observations. As a result of these calculations we estimate iron abundance, hydrogen density and photoionizing flux in quasar environment. Although the result suggests that the iron has solar abundance in the PG 1626+554, more accurate observations are needed to confirm this conclusion. This work was initiated while EV visit at NAOJ/IoA-UT as a NAOJ COE visiting professor. EV research and travel to AAS is supported by the National Science Foundation (NSF 0206150) program. We acknowledge the set of HST/FOS observations.
56.
T. Murayama, Y. Shioya, Y. Taniguchi, M. Ajiki, T. Nagao, S. S. Fujita, Y. Kakazu, Y. Komiyama, S. Okamura, Shinki Oyabu, K. Kawara, Y. Ohyama, S. K. Kawabata, H. Ando, T. Nishimura, M. Hayashi, R. Ogasawara and S. Ichikawa : SDSSp J104433.04-012502.2 at z=5.74 is Gravitationally Magnified by an Intervening Galaxy, 8th Asian-Pacific Regional Meeting, Volume II, 481, 2002.
(要約)
During the course of our optical deep survey program on Lyα emitters at z ? 5.7 in the sky area surrounding the quasar SDSSp J104433.04-012502.2 at z=5.74, we have found that a faint galaxy with mB(AB) ? 25 is located at 1.9 arcsec southwest of the quasar. Its broad band color properties from B to z' suggest that the galaxy is located at a redshift of z ? 1.5 -- 2.5. This is consistent with no strong emission line in our optical spectroscopy. Since the counter image of the quasar cannot be seen in our deep optical images, the magnification factor seems not so high. Our modest estimate is that this quasar is gravitationally magnified by a factor of 2.
57.
Shinki Oyabu : Spectroscopic investigation of ISO far-infrared sources, Subaru Proposal, 104, 2001.
A delay of ~ 1.5 Gyr in Fe enrichment, relative to Mg ((alpha) element), might provide a chronometer for measuring the age of quasars and then constraining the age of the Universe. We are carrying out a project to do spectroscopy of many quasars from low-redshift to high-redshift in order to obtain the relation of the FeII/MgII flux ratio versus redshift. Combining this relation with the models of chemical evolution of galaxies, we would be able to know:(1)whether or not Fe is overabundant in broad-line gas of low-redshift quasars, (2)how quasar host galaxies formed, (3)the epoch of host galaxy formation, (4)the age of quasars, and eventually (5)the age of the Universe. As part of this project, we propose to do optical spectroscopy of 20 low- redshift quasars by using the GoldCam Spectrometer on KPNO-2.1m telescope. These optical spectra will be combined FOS UV spectra to extract broad FeII emission feature in the UV.
59.
S. M. Yun, D. Sanders, K. Kawara, Shinki Oyabu, Y. Taniguchi and H. Okuda : Radio Study of the Lockman Hole ISOPHOT Survey Sources, Gas and Galaxy Evolution, Vol.240, 123, 2001.
(要約)
One of the most exciting discoveries made by the Infrared Space Observatory (ISO) was the detection of a substantial excess in the number density of faint far-infrared (95 μm & 175 μm) sources, suggesting strong cosmological evolution in the population of luminous infrared galaxies. The number density of 175μm sources derived from two deep fields (each 44' × 44') in the Lockman Hole region is >?10 times larger than predicted from no-evolution models. Several lines of reasoning suggest that the majority of the faint ISOPHOT sources may be at modest redshift (z<?1), and the ISOPHOT sources appear to bridge the gap between the starburst galaxies in the local universe and z>=2 obscured starbursts detected by the SCUBA surveys. We have carried out deep, high-resolution 1.4 GHz observations of the ISOPHOT survey fields using the VLA as part of a multi-wavelength follow-up study. In concert with deep optical and near-infrared (B, V, R, I, K) imaging, individual ISOPHOT sources are identified using high-resolution radio continuum images. Spectroscopic observations to determine the redshift and the nature of the powering sources are currently underway. Combined with ongoing SCUBA observations, photometric redshifts may be obtained even for sources that are heavily obscured. We are also investigating the nature of a radio selected galaxy sample using the same multi-wavelength database.
60.
Shinki Oyabu : Spectroscopic Investigation of the ISO far-infrared sources, Subaru Proposal, 2, 2001.
61.
Shinki Oyabu, K. Kawara, Y. Tsuzuki, Y. Sofue, Y. Sato, H. Okuda, Y. Taniguchi, H. Shibai, C. Gabriel, T. Hasegawa and E. Nishihara : ISO Continuum Observations of Quasars at z =1-4, Mid- and Far-Infrared Astronomy and Future Space Missions, 139, 2000.
Angel Castro, Takamitsu Miyaji, A. Matthew Malkan, Kohei Ichikawa, Yoshihiro Ueda, M. Shirahata, Takao Nakagawa, Masatoshi Imanishi and Shinki Oyabu : Mid- and Near-infrared spectral properties of a sample of Swift-BAT X-ray selected AGNs, IAU General Assembly, Vol.29, 2257931, Aug. 2015.
(要約)
We present a comparative study of the mid- (MIR) to near-infrared (NIR) properties of a sample of X-ray selected AGNs from the Swift/Burst Alert Telescope (BAT) 70-month all-sky hard X-ray (14-195 keV) survey. For a sample of 78 AGNs, including both Seyfert 1 and Seyfert 2 sources with black hole masses derived from 2MASS K-band magnitudes and literature, we obtain spectroscopic data from the IRC (2.5 - 5 μm) and IRS (in the 5-14 μm band) instruments onboard the Akari and Spitzer satellites, respectively. We test possible correlations between the 3.3, 6.2, 7.7, 8.6, 11.2 and 12.7 μm polycyclic aromatic hydrocarbon (PAH) emission features, the continuum slope and CO optical depth, as well as CO2, H2O, and amorphous silicates. Using the 3.3, 6.2 and 11.3 μm PAH emission features as a proxy for the star-formation rate (SFR) we report the AGN type and Eddington-ratio dependences of circum-nuclear star formation.
大薮 進喜, 鈴木 仁研, 和田 武彦, 金田 英宏, 下村 太誉, 小田切 萌絵, K D. Ojha, A. S. L. D'Costa, S. Ghosh, R. P. Sandimani : 大質量星形成領域の遠赤外線 [CII] 輝線広域観測を進める日印共同気球実験, 日本天文学会2022年春季年会, 2020年3月.
The Cosmic Optical Background (COB) constitutes vital information on formation of galaxies, AGNs, and large-scale structure, since it records the total emission from stars in galaxies and any light-emitting materials in intergalactic space, if any, over all time after z ~ 6. Here, we propose to do B- and R-band imaging over an area of 50 square degrees covering the CO cloud and the minimum HI column density points in the Lockman Hole. These optical data will be combined with the diffuse far-infrared maps of the Akari satellite. Utilizing the shielding effect of dark clouds on optical light and the correlation between the optical scattered light and the far-infrared emission, we will observe the COB. The proposed observation is useful for other studies: (1) distribution of interstellar dust; (2) optical properties of dust grain in the optical and far-infrared such as extinction coefficients and size distribution of dust; (3) reducing the confusion noise by IR cirrus when searching for faint far-infrared galaxies.
2.
Shinki Oyabu, Daisuke Ishihara, Takehiko Wada, Youichi Ohyama, Satoshi Takaita, Hideo Matsuhara, Takashi Onaka, Hirokazu Kataza, Myungshin Im and Matt Malkan : New survey for Active Galactic Nuclei using AKARI mid-infrared all sky survey, NOAO Proposal, 399, Feb. 2009.
(要約)
We propose new survey for Active Galactic Nuclei using AKARI mid- infrared (MIR) all sky survey. The AGN selection in the mid-infrared can minimize wavelength-dependent selection effects. Using this sample, we can make the unbiased statistical studies that answer how much the space density of Seyfert 1 and Seyfert 2 is, what kind of galaxies the hosts of AGNs are and so on. The AKARI MIR all sky survey was carried out with two wide bands of the Infrared Camera (IRC) centered at 9 and 18 micron with the sensitivity of about 50 and 120 mJy (5-sigma per scan), respectively. The AKARI mid-infrared all-sky survey substantially improves the MIR data set of the IRAS survey of two decades ago. Our targets are selected with a criterion of F(9 micron)/F(K_S) >2 that culls AGN candidates from MIR all sky survey. In this semester, our 40 targets have been selected in the North Galactic Cap. We request four nights with KPNO 2.1m/Goldman Spectrograph for spectroscopic in order to measure their redshift and to confirm their activities.
3.
Myungshin Im, Mok Hyung Lee, Gyoon Myung Lee, Hideo Matsuhara, Takehiko Wada, Shinki Oyabu and Akari Survey Nep Team : NIR Imaging of the AKARI North Ecliptic Pole Wide Survey Field, NOAO Proposal, 242, Feb. 2008.
(要約)
We propose to perform J- and H-band wide-field imaging of the north ecliptic pole (NEP) area which has been surveyed by the AKARI Infrared Space Telescope. The NEP-Wide survey, one of the AKARI's key scientific programs, images a 5.8 deg^2 circular area centered on the north ecliptic pole with contiguous 9 passbands between 2.5 and 24 (micron) to the flux limit ranging from 15 (mu)Jy to 500 (mu)Jy (plus FIR data), including 11, 15, and 18 (micron) bands where the Spitzer has limitations. Thus, NEP-Wide is the only wide-area IR survey that allows us to study the evolution of various mid-IR features from z=0 to z=2 such as PAHs, silicate absorptions, and power-slopes of AGNs, and their connection to IR-luminosity, star formation and AGN activities of IR sources not bright enough for the Spitzer spectroscopy. Optical imaging as well as radio/X-ray data exist over this field, however there is a gaping hole at NIR between the AKARI and the optical coverage. In order to fill the wavelength gap, we propose to obtain J-, and H-band images to 15 (mu)Jy at 5-ς using FLAMINGOS on the 2.1-m. Filling the hole in the spectral energy distribution will significantly increase the value of the NEP-Wide dataset by permitting us to add more accurate stellar mass and photo-z estimates, and also a large number of SEDs from optical to IR without a gap in wavelength coverage.
4.
A. B. Peterson, Shinki Oyabu and Y. Hamada : GRB040709 J,H-band observations., GRB Coordinates Network, Vol.2624, 1, Jan. 2004.
5.
S. Min Yun, Dave Sanders, Kimiaki Kawara, Shinki Oyabu, Yoshiaki Taniguchi, Takashi Murayama and Yasunori Sato : Spectroscopic investigation of the ISO far-IR (175(micron) & 95(mu)m) sources, NOAO Proposal, 150, Feb. 2002.
(要約)
We propose to carry out spectroscopic observations of a large sample of far-infrared (FIR) sources identified in the deep Infrared Space Observatory far-infrared survey of the Lockman Hole region using HYDRR on the WIYN telescope. A comparison of the ISOPHOT sources with radio and X-ray data suggests that most of the FIR sources are star-forming galaxies rather than AGNs. The number density of ISOPHOT sources exceeds the predictions of the star formation evolution models based on optical data. Substantial dust obscuration of star forming activity may be occurring even at modest redshifts, where most of these ISOPHOT sources are expected to be located. Our proposed multi-object spectroscopy with HYDRR will help determine the redshifts and luminosity for the bulk of the ISOPHOT sources. Our proposed WIYN observations will enable us for the first time to constrain the contribution of far-infrared galaxies to the star formation history of the Universe over the important redshift range z=0-1.5 where the SFR appears to increase by as much as a factor of 20-100 compared to the current epoch, and where as much as 50-80% of the luminosity is hidden by dust.
6.
Shinki Oyabu : Optical morphology of ISO far-infrared sources in the Lockman Hole seen through 0.5" resolution imaging, Subaru Proposal, 8, Jan. 2000.