TERASHIMA, Yuichi

Faculty
Graduate School of Science and Engineering Mathematics Physics and Earth Sciences
PositionProfessor
Mailterashima.yuichi.mc[at]ehime-u.ac.jp In case of sending E-mail, please alternate [at] to @
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Birthday
Last Updated :2017/08/18

Researcher Profile and Settings

Association Memberships

  • American Astronomical Society
  • International Astronomical Union

Research Activities

Misc

  • Hitomi Constraints on the 3.5 keV Line in the Perseus Galaxy Cluster
    F. A. Aharonian, F. A. Aharonian, H. Akamatsu, F. Akimoto, S. W. Allen, S. W. Allen, S. W. Allen, L. Angelini, K. A. Arnaud, K. A. Arnaud, M. Audard, H. Awaki, M. Axelsson, A. Bamba, M. W. Bautz, R. D. Blandford, R. D. Blandford, R. D. Blandford, E. Bulbul, L. W. Brenneman, G. V. Brown, E. M. Cackett, M. Chernyakova, M. P. Chiao, P. Coppi, E. Costantini, J. De Plaa, J. W.Den Herder, C. Done, T. Dotani, K. Ebisawa, M. E. Eckart, T. Enoto, T. Enoto, Y. Ezoe, A. C. Fabian, C. Ferrigno, A. R. Foster, R. Fujimoto, Y. Fukazawa, A. Furuzawa, M. Galeazzi, L. C. Gallo, P. Gandhi, M. Giustini, A. Goldwurm, L. Gu, M. Guainazzi, M. Guainazzi, Y. Haba, K. Hagino, K. Hamaguchi, K. Hamaguchi, I. Harrus, I. Harrus, I. Hatsukade, K. Hayashi, T. Hayashi, K. Hayashida, J. Hiraga, A. E. Hornschemeier, A. Hoshino, J. P. Hughes, Y. Ichinohe, R. Iizuka, H. Inoue, S. Inoue, Y. Inoue, K. Ishibashi, M. Ishida, K. Ishikawa, Y. Ishisaki, M. Itoh, M. Iwai, N. Iyomoto, J. S. Kaastra, T. Kallman, T. Kamae, E. Kara, J. Kataoka, S. Katsuda, J. Katsuta, M. Kawaharada, N. Kawai, R. L. Kelley, D. Khangulyan, C. A. Kilbourne, A. L. King, A. L. King, T. Kitaguchi, S. Kitamoto, T. Kitayama, T. Kohmura, M. Kokubun, S. Koyama, K. Koyama, P. Kretschmar, H. A. Krimm, H. A. Krimm, A. Kubota, Astrophysical Journal Letters, 837,   2017 03 01 , © 2017. The American Astronomical Society. All rights reserved.High-resolution X-ray spectroscopy with Hitomi was expected to resolve the origin of the faint unidentified E ≈ 3.5 keV emission line reported in several low-resolution studies of various massive systems, such as galaxies and clusters, including the Perseus cluster. We have analyzed the Hitomi first-light observation of the Perseus cluster. The emission line expected for Perseus based on the XMM-Newton signal from the large cluster sample under the dark matter decay scenario is too faint to be detectable in the Hitomi data. However, the previously reported 3.5 keV flux from Perseus was anomalously high compared to the sample-based prediction. We find no unidentified line at the reported high flux level. Taking into account the XMM measurement uncertainties for this region, the inconsistency with Hitomi is at a 99% significance for a broad dark matter line and at 99.7% for a narrow line from the gas. We do not find anomalously high fluxes of the nearby faint K line or the Ar satellite line that were proposed as explanations for the earlier 3.5 keV detections. We do find a hint of a broad excess near the energies of high-n transitions of S xvi (E ≃ 3.44 keV rest-frame) - a possible signature of charge exchange in the molecular nebula and another proposed explanation for the unidentified line. While its energy is consistent with XMM pn detections, it is unlikely to explain the MOS signal. A confirmation of this interesting feature has to wait for a more sensitive observation with a future calorimeter experiment.
  • Shedding Light on the Compton-thick Active Galactic Nucleus in the Ultraluminous Infrared Galaxy UGC 5101 with Broadband X-Ray Spectroscopy
    Saeko Oda, Atsushi Tanimoto, Yoshihiro Ueda, Masatoshi Imanishi, Masatoshi Imanishi, Masatoshi Imanishi, Yuichi Terashima, Claudio Ricci, Claudio Ricci, Astrophysical Journal, 835,   2017 02 01 , © 2017. The American Astronomical Society. All rights reserved.We report the broadband X-ray spectra of the ultraluminous infrared galaxy (ULIRG) UGC 5101 in the 0.25-100 keV band observed with the Swift/Burst Alert Telescope (BAT), Nuclear Spectroscopic Telescope Array (NuSTAR), Suzaku, XMM-Newton, and Chandra. A Compton-thick active galactic nucleus (AGN) obscured with a hydrogen column density of ≈ 1.3 × 102 cm-2 is detected above 10 keV. A spectral fit with a numerical torus model favors a large half-opening angle of the torus, >41°, suggesting that the covering fraction of material heavily obscuring the X-ray source is moderate. The intrinsic 2-10 keV luminosity is determined to be ≈ 1.4 × 1043 erg s-1, which is ≈2.5 times larger than the previous estimate using only data below 10 keV with a simple spectral model. We find that UGC 5101 shows the ratio between the [O iv] 26 μm line and 2-10 keV luminosities similar to those of normal Seyfert galaxies, along with other ULIRGs observed with NuSTAR, indicating that a significant portion of local ULIRGs are not really "X-ray faint" with respect to the flux of forbidden lines originating from the narrow-line region. We propose a possible scenario that (1) the AGN in UGC 5101 is surrounded not only by Compton-thick matter located close to the equatorial plane but also by Compton-thin (NH ∼ 1021 cm-2) matter in the torus-hole region and (2) it is accreting at a high Eddington rate with a steep UV to X-ray spectral energy distribution. Nevertheless, we argue that AGNs in many ULIRGs do not look extraordinary (i.e., extremely X-ray faint), as suggested by recent works, compared with normal Seyferts.
  • CLUSTERING of INFRARED-BRIGHT DUST-OBSCURED GALAXIES REVEALED by the HYPER SUPRIME-CAM and WISE
    Yoshiki Toba, Yoshiki Toba, Tohru Nagao, Masaru Kajisawa, Masaru Kajisawa, Taira Oogi, Masayuki Akiyama, Hiroyuki Ikeda, Jean Coupon, Michael A. Strauss, Wei Hao Wang, Masayuki Tanaka, Mana Niida, Masatoshi Imanishi, Masatoshi Imanishi, Chien Hsiu Lee, Chien Hsiu Lee, Hideo Matsuhara, Hideo Matsuhara, Yoshiki Matsuoka, Yoshiki Matsuoka, Masafusa Onoue, Masafusa Onoue, Yuichi Terashima, Yuichi Terashima, Yoshihiro Ueda, Yuichi Harikane, Yuichi Harikane, Yutaka Komiyama, Yutaka Komiyama, Satoshi Miyazaki, Satoshi Miyazaki, Akatoki Noboriguchi, Tomonori Usuda, Tomonori Usuda, Astrophysical Journal, 835,   2017 01 20 , © 2017. The American Astronomical Society. All rights reserved.We present measurements of the clustering properties of a sample of infrared (IR) bright dust-obscured galaxies (DOGs). Combining 125 deg2 of wide and deep optical images obtained with the Hyper Suprime-Cam on the Subaru Telescope and all-sky mid-IR images taken with Wide-Field Infrared Survey Explorer, we have discovered 4367 IR-bright DOGs with and flux density at 22 mJy. We calculate the angular autocorrelation function (ACF) for a uniform subsample of 1411 DOGs with 3.0 mJy < flux (22 ) < 5.0 mJy and < 24.0. The ACF of our DOG subsample is well-fit with a single power law, ω(θ)=(0.010 ± 0.003) , where θ is in degrees. The correlation amplitude of IR-bright DOGs is larger than that of IR-faint DOGs, which reflects a flux dependence of the DOG clustering, as suggested by Brodwin et al. We assume that the redshift distribution for our DOG sample is Gaussian, and consider two cases: (1) the redshift distribution is the same as IR-faint DOGs with flux at 22 < 1.0 mJy, mean and sigma z = 1.99 ±0.45, and (2) z = 1.19 ±0.30, as inferred from their photometric redshifts. The inferred correlation length of IR-bright DOGs is r 0 = 12.0 ±2.0 and 10.3 ±1.7 Mpc, respectively. IR-bright DOGs reside in massive dark matter halos with a mass of log[〈Mh〉 /(h-1M⊙)]13.57-0.55+0.50 and 13.65+0.45-0.52 in the two cases, respectively.
  • STUDY of SWIFT/BAT SELECTED LOW-LUMINOSITY ACTIVE GALACTIC NUCLEI OBSERVED with SUZAKU
    Taiki Kawamuro, Yoshihiro Ueda, Fumie Tazaki, Yuichi Terashima, Richard Mushotzky, Astrophysical Journal, 831,   2016 11 01 , © 2016. The American Astronomical Society. All rights reserved.We systematically analyze the broadband (0.5-200 keV) X-ray spectra of hard X-ray (>10 keV) selected local low-luminosity active galactic nuclei (LLAGNs) observed with Suzaku and Swift/BAT. The sample consists of 10 LLAGNs detected with Swift/BAT with intrinsic 14-195 keV luminosities smaller than 1042 erg s-1 available in the Suzaku archive, covering a wide range of the Eddington ratio from 10-5 to 10-2. The overall spectra can be reproduced with an absorbed cut-off power law, often accompanied by reflection components from distant cold matter, and/or optically thin thermal emission from the host galaxy. In all of the objects, relativistic reflection components from the innermost disk are not required. Eight objects show a significant narrow iron-Kα emission line. Comparing their observed equivalent widths with the predictions from the Monte-Carlo-based torus model by Ikeda et al. (2009), we constrain the column density in the equatorial plane to be NHeq > 22.7, or the torus half-opening angle θoa < 70°. We infer that the Eddington ratio (λEdd) is a key parameter that determines the torus structure of LLAGNs: the torus becomes large at λEdd ≳ 2 × 10-4, whereas at lower accretion rates it is little developed. The luminosity correlation between the hard X-ray and mid-infrared (MIR) bands of the LLAGNs follows the same correlation as for more luminous AGNs. This implies that mechanisms other than AGN-heated dust are responsible for the MIR emission in low Eddington ratio LLAGNs.
  • The quiescent intracluster medium in the core of the Perseus cluster
    Felix Aharonian, Felix Aharonian, Hiroki Akamatsu, Fumie Akimoto, Steven W. Allen, Steven W. Allen, Steven W. Allen, Naohisa Anabuki, Lorella Angelini, Keith Arnaud, Keith Arnaud, Marc Audard, Hisamitsu Awaki, Magnus Axelsson, Aya Bamba, Marshall Bautz, Roger Blandford, Roger Blandford, Roger Blandford, Laura Brenneman, Gregory V. Brown, Esra Bulbul, Edward Cackett, Maria Chernyakova, Meng Chiao, Paolo Coppi, Elisa Costantini, Jelle De Plaa, Jan Willem Den Herder, Chris Done, Tadayasu Dotani, Ken Ebisawa, Megan Eckart, Teruaki Enoto, Teruaki Enoto, Yuichiro Ezoe, Andrew C. Fabian, Carlo Ferrigno, Adam Foster, Ryuichi Fujimoto, Yasushi Fukazawa, Akihiro Furuzawa, Massimiliano Galeazzi, Luigi Gallo, Poshak Gandhi, Margherita Giustini, Andrea Goldwurm, Liyi Gu, Matteo Guainazzi, Matteo Guainazzi, Yoshito Haba, Kouichi Hagino, Kenji Hamaguchi, Kenji Hamaguchi, Ilana Harrus, Ilana Harrus, Isamu Hatsukade, Katsuhiro Hayashi, Takayuki Hayashi, Kiyoshi Hayashida, Junko Hiraga, Ann Hornschemeier, Akio Hoshino, John Hughes, Ryo Iizuka, Hajime Inoue, Yoshiyuki Inoue, Kazunori Ishibashi, Manabu Ishida, Kumi Ishikawa, Yoshitaka Ishisaki, Masayuki Itoh, Naoko Iyomoto, Jelle Kaastra, Timothy Kallman, Tuneyoshi Kamae, Erin Kara, Jun Kataoka, Satoru Katsuda, Junichiro Katsuta, Madoka Kawaharada, Nobuyuki Kawai, Richard Kelley, Dmitry Khangulyan, Caroline Kilbourne, Ashley King, Ashley King, Takao Kitaguchi, Shunji Kitamoto, Tetsu Kitayama, Takayoshi Kohmura, Motohide Kokubun, Shu Koyama, Katsuji Koyama, Peter Kretschmar, Hans Krimm, Hans Krimm, Aya Kubota, Hideyo Kunieda, Philippe Laurent, Nature, 535,   2016 07 06 , © 2016 Macmillan Publishers Limited. All rights reserved.Clusters of galaxies are the most massive gravitationally bound objects in the Universe and are still forming. They are thus important probes of cosmological parameters and many astrophysical processes. However, knowledge of the dynamics of the pervasive hot gas, the mass of which is much larger than the combined mass of all the stars in the cluster, is lacking. Such knowledge would enable insights into the injection of mechanical energy by the central supermassive black hole and the use of hydrostatic equilibrium for determining cluster masses. X-rays from the core of the Perseus cluster are emitted by the 50-million-kelvin diffuse hot plasma filling its gravitational potential well. The active galactic nucleus of the central galaxy NGC 1275 is pumping jetted energy into the surrounding intracluster medium, creating buoyant bubbles filled with relativistic plasma. These bubbles probably induce motions in the intracluster medium and heat the inner gas, preventing runaway radiative cooling - a process known as active galactic nucleus feedback. Here we report X-ray observations of the core of the Perseus cluster, which reveal a remarkably quiescent atmosphere in which the gas has a line-of-sight velocity dispersion of 164 ± 10 kilometres per second in the region 30-60 kiloparsecs from the central nucleus. A gradient in the line-of-sight velocity of 150 ± 70 kilometres per second is found across the 60-kiloparsec image of the cluster core. Turbulent pressure support in the gas is four per cent of the thermodynamic pressure, with large-scale shear at most doubling this estimate. We infer that a total cluster mass determined from hydrostatic equilibrium in a central region would require little correction for turbulent pressure.
  • SUZAKU OBSERVATIONS of MODERATELY OBSCURED (Compton-THIN) ACTIVE GALACTIC NUCLEI SELECTED by SWIFT/BAT HARD X-RAY SURVEY
    Taiki Kawamuro, Yoshihiro Ueda, Fumie Tazaki, Claudio Ricci, Claudio Ricci, Yuichi Terashima, Astrophysical Journal, Supplement Series, 225,   2016 07 01 , © 2016. The American Astronomical Society. All rights reserved.We report the results obtained by a systematic, broadband (0.5-150 keV) X-ray spectral analysis of moderately obscured (Compton-thin, 22 ≤ logNH < 24) active galactic nuclei (AGNs) observed with Suzaku and Swift/Burst Alert Telescope (BAT). Our sample consists of 45 local AGNs at z < 0.1 with log L14-195 keV > 42 detected in the Swift/BAT 70-month survey, whose Suzaku archival data are available as of 2015 December. All spectra are uniformly fit with a baseline model composed of an absorbed cutoff power-law component, reflected emission accompanied by a narrow fluorescent iron-Kα line from cold matter (torus), and scattered emission. The main results based on the above analysis are as follows. (1) The photon index is correlated with Eddington ratio, but not with luminosity or black hole mass. (2) The ratio of the luminosity of the iron-Kα line to the X-ray luminosity an indicator of the covering fraction of the torus, shows significant anticorrelation with luminosity. (3) The averaged reflection strength derived from stacked spectra above 14 keV is larger in less luminous (log L10-50 keV ≤ 43.3, R = 1.04-0.19+0.17) or highly obscured (logNH > 23 , = R 1.03-0.17+0.15) AGNs than in more luminous (log L10-50 keV > 43.3, = R 0.46-0.09+0.08) or lightly obscured (logNH 23, = - R 0.59-0.10+0.09) objects. (4) The ratio of the luminosity of the [O IV] 25.89 μm line to the X-ray luminosity is significantly smaller in AGNs with lower soft X-ray scattering fractions, suggesting that the former luminosity underestimates the intrinsic power of an AGN buried in a torus of small opening angle.
  • SUBMILLIMETER-HCN DIAGRAM FOR ENERGY DIAGNOSTICS IN THE CENTERS OF GALAXIES
    Takuma Izumi, Kotaro Kohno, Kotaro Kohno, Susanne Aalto, Daniel Espada, Daniel Espada, Daniel Espada, Kambiz Fathi, Nanase Harada, Bunyo Hatsukade, Pei Ying Hsieh, Pei Ying Hsieh, Masatoshi Imanishi, Masatoshi Imanishi, Masatoshi Imanishi, Melanie Krips, Sergio Martín, Sergio Martín, Sergio Martín, Satoki Matsushita, David S. Meier, Naomasa Nakai, Kouichiro Nakanishi, Kouichiro Nakanishi, Kouichiro Nakanishi, Eva Schinnerer, Kartik Sheth, Yuichi Terashima, Jean L. Turner, Astrophysical Journal, 818,   2016 02 10 , © 2016. The American Astronomical Society. All rights reserved.Compiling data from literature and the Atacama Large Millimeter/submillimeter Array archive, we show enhanced HCN(4-3)/HCO+(4-3) and/or HCN(4-3)/CS(7-6) integrated intensity ratios in circumnuclear molecular gas around active galactic nuclei (AGNs) compared to those in starburst (SB) galaxies (submillimeter HCN enhancement). The number of sample galaxies is significantly increased from our previous work. We expect that this feature could potentially be an extinction-free energy diagnostic tool of nuclear regions of galaxies. Non-LTE radiative transfer modelings of the above molecular emission lines involving both collisional and radiative excitation, as well as a photon trapping effect, were conducted to investigate the cause of the high line ratios in AGNs. As a result, we found that enhanced abundance ratios of HCN to HCO+ and HCN to CS in AGNs as compared to SB galaxies by a factor of a few to even ≳10 are a plausible explanation for the submillimeter HCN enhancement. However, a counterargument of a systematically higher gas density in AGNs than in SB galaxies can also be a plausible scenario. Although we cannot fully distinguish these two scenarios at this moment owing to an insufficient amount of multi-transition, multi-species data, the former scenario is indicative of abnormal chemical composition in AGNs. Regarding the actual mechanism to realize the composition, we suggest that it is difficult with conventional gas-phase X-ray-dominated region ionization models to reproduce the observed high line ratios. We might have to take into account other mechanisms such as neutral-neutral reactions that are efficiently activated in high-temperature environments and/or mechanically heated regions to further understand the high line ratios in AGNs.
  • The ASTRO-H (Hitomi) X-ray astronomy satellite
    Tadayuki Takahashi, Motohide Kokubun, Kazuhisa Mitsuda, Richard Kelley, Takaya Ohashi, Felix Aharonian, Hiroki Akamatsu, Fumie Akimoto, Steve Allen, Naohisa Anabuki, Lorella Angelini, Keith Arnaud, Makoto Asai, Marc Audard, Hisamitsu Awaki, Magnus Axelsson, Philipp Azzarello, Chris Baluta, Aya Bamba, Nobutaka Bando, Marshall Bautz, Thomas Bialas, Roger Blandford, Kevin Boyce, Laura Brenneman, Greg Brown, Esra Bulbul, Edward Cackett, Edgar Canavan, Maria Chernyakova, Meng Chiao, Paolo Coppi, Elisa Costantini, Jelle De Plaa, Jan Willem Den Herder, Michael DiPirro, Chris Done, Tadayasu Dotani, John Doty, Ken Ebisawa, Megan Eckart, Teruaki Enoto, Yuichiro Ezoe, Andrew Fabian, Carlo Ferrigno, Adam Foster, Ryuichi Fujimoto, Yasushi Fukazawa, Akihiro Furuzawa, Massimiliano Galeazzi, Luigi Gallo, Poshak Gandhi, Kirk Gilmore, Margherita Giustini, Andrea Goldwurm, Liyi Gu, Matteo Guainazzi, Daniel Haas, Yoshito Haba, Kouichi Hagino, Kenji Hamaguchi, Atsushi Harayama, Ilana Harrus, Isamu Hatsukade, Takayuki Hayashi, Katsuhiro Hayashi, Kiyoshi Hayashida, Junko Hiraga, Kazuyuki Hirose, Ann Hornschemeier, Akio Hoshino, John Hughes, Yuto Ichinohe, Ryo Iizuka, Yoshiyuki Inoue, Hajime Inoue, Kazunori Ishibashi, Manabu Ishida, Kumi Ishikawa, Kosei Ishimura, Yoshitaka Ishisaki, Masayuki Itoh, Naoko Iwata, Naoko Iyomoto, Chris Jewell, Jelle Kaastra, Timothy Kallman, Tuneyoshi Kamae, Erin Kara, Jun Kataoka, Satoru Katsuda, Junichiro Katsuta, Madoka Kawaharada, Nobuyuki Kawai, Taro Kawano, Shigeo Kawasaki, Dmitry Khangulyan, Caroline Kilbourne, Mark Kimball, Ashley King, Proceedings of SPIE - The International Society for Optical Engineering, 9905,   2016 01 01 , © 2016 SPIE.The Hitomi (ASTRO-H) mission is the sixth Japanese X-ray astronomy satellite developed by a large international collaboration, including Japan, USA, Canada, and Europe. The mission aimed to provide the highest energy resolution ever achieved at E > 2 keV, using a microcalorimeter instrument, and to cover a wide energy range spanning four decades in energy from soft X-rays to gamma-rays. After a successful launch on 2016 February 17, the spacecraft lost its function on 2016 March 26, but the commissioning phase for about a month provided valuable information on the on-board instruments and the spacecraft system, including astrophysical results obtained from first light observations. The paper describes the Hitomi (ASTRO-H) mission, its capabilities, the initial operation, and the instruments/spacecraft performances confirmed during the commissioning operations for about a month.
  • λ5007 and X-RAY PROPERTIES of A COMPLETE SAMPLE of HARD X-RAY SELECTED AGNs in the LOCAL UNIVERSE
    Y. Ueda, Y. Hashimoto, K. Ichikawa, K. Ichikawa, Y. Ishino, A. Y. Kniazev, A. Y. Kniazev, A. Y. Kniazev, P. Väisänen, P. Väisänen, C. Ricci, C. Ricci, C. Ricci, S. Berney, P. Gandhi, M. Koss, R. Mushotzky, Y. Terashima, B. Trakhtenbrot, M. Crenshaw, Astrophysical Journal, 815,   2015 12 10 , © 2015. The American Astronomical Society. All rights reserved.We study the correlation between the [O iii] λ5007 and X-ray luminosities of local active galactic nuclei (AGNs), using a complete, hard X-ray (>10 keV) selected sample in the Swift/BAT 9-month catalog. From our optical spectroscopic observations at the South African Astronomical Observatory and the literature, a catalog of [O iii] λ5007 line flux for all 103 AGNs at Galactic latitudes of is compiled. Significant correlations with intrinsic X-ray luminosity () are found for both observed () and extinction-corrected () luminosities, separately for X-ray unabsorbed and absorbed AGNs. We obtain the regression form of and from the whole sample. The absorbed AGNs with low (<0.5%) scattering fractions in soft X-rays show on average smaller and ratios than the other absorbed AGNs, while those in edge-on host galaxies do not. These results suggest that a significant fraction of thisopulation is buried in tori with small opening angles. By using these versus correlations, the X-ray luminosity function (LF) of local AGNs (including Compton-thick AGNs) in a standardopulation synthesis model gives much better agreement with the [O iii] λ5007 LF derived from the Sloan Digital Sky Survey thanreviously reported. This confirms that hard X-ray observations are a veryowerful tool to find AGNs with high completeness.
  • A new sample of obscured agns selected from the XMM-Newton and AKARI surveys
    Yuichi Terashima, Yoshitaka Hirata, Hisamitsu Awaki, Shinki Oyabu, Poshak Gandhi, Yoshiki Toba, Hideo Matsuhara, Astrophysical Journal, 814,   2015 11 20 , © 2015. The American Astronomical Society. All rights reserved.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 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/ or CR/ 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 ∼ 1022-24 cm-2, a very flat continuum, or a strong Fe-K emission line with an equivalent width of 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.
  • ALMA OBSERVATIONS of the SUBMILLIMETER DENSE MOLECULAR GAS TRACERS in the LUMINOUS TYPE-1 ACTIVE NUCLEUS of NGC 7469
    Takuma Izumi, Kotaro Kohno, Kotaro Kohno, Susanne Aalto, Akihiro Doi, Daniel Espada, Daniel Espada, Daniel Espada, Kambiz Fathi, Nanase Harada, Bunyo Hatsukade, Takashi Hattori, Takashi Hattori, Pei Ying Hsieh, Pei Ying Hsieh, Soh Ikarashi, Soh Ikarashi, Masatoshi Imanishi, Masatoshi Imanishi, Masatoshi Imanishi, Daisuke Iono, Daisuke Iono, Sumio Ishizuki, Melanie Krips, Sergio Martín, Satoki Matsushita, David S. Meier, Hiroshi Nagai, Naomasa Nakai, Taku Nakajima, Kouichiro Nakanishi, Kouichiro Nakanishi, Kouichiro Nakanishi, Hideko Nomura, Michael W. Regan, Eva Schinnerer, Kartik Sheth, Shuro Takano, Yoichi Tamura, Yuichi Terashima, Tomoka Tosaki, Jean L. Turner, Hideki Umehata, Tommy Wiklind, Astrophysical Journal, 811,   2015 09 20 , © 2015. The American Astronomical Society. All rights reserved..We present Atacama Large Millimeter/submillimeter Array (ALMA) Cycle 1 observations of the central kiloparsec region of the luminous type 1 Seyfert galaxy NGC 7469 with unprecedented high resolution (0.″5 e×0.″4 = 165 e× 132 pc) at submillimeter wavelengths. Utilizing the wide bandwidth of ALMA, we simultaneously obtained HCN(4-3), HCO+(4-3), CS(7-6), and partially CO(3-2) line maps, as well as the 860 μm continuum. The region consists of the central ∼1″ component and the surrounding starburst ring with a radius of ∼1.″5-2.″5. Several structures connect these components. Except for CO(3-2), these dense gas tracers are significantly concentrated toward the central ∼1″, suggesting their suitability to probe the nuclear regions of galaxies. Their spatial distribution resembles well those of centimeter and mid-infrared continuum emissions, but it is anticorrelated with the optical one, indicating the existence of dust-obscured star formation. The integrated intensity ratios of HCN(4-3)/HCO+(4-3) and HCN(4-3)/CS(7-6) are higher at the active galactic nucleus (AGN) position than at the starburst ring, which is consistent with our previous findings (submillimeter-HCN enhancement). However, the HCN(4-3)/HCO+(4-3) ratio at the AGN position of NGC 7469 (1.11 0.06) is almost half of the corresponding value of the low-luminosity type 1 Seyfert galaxy NGC 1097 (2.0 0.2), despite the more than two orders of magnitude higher X-ray luminosity of NGC 7469. But the ratio is comparable to that of the close vicinity of the AGN of NGC 1068 (∼1.5). Based on these results, we speculate that some heating mechanisms other than X-ray (e.g., mechanical heating due to an AGN jet) can contribute significantly for shaping the chemical composition in NGC 1097.
  • LOCAL INSTABILITY SIGNATURES IN ALMA OBSERVATIONS OF DENSE GAS IN NGC 7469
    Kambiz Fathi, Kambiz Fathi, Takuma Izumi, Alessandro B. Romeo, Sergio Martín, Masatoshi Imanishi, Masatoshi Imanishi, Masatoshi Imanishi, Evanthia Hatziminaoglou, Susanne Aalto, Daniel Espada, Daniel Espada, Daniel Espada, Kotaro Kohno, Kotaro Kohno, Melanie Krips, Satoki Matsushita, David S. Meier, Naomasa Nakai, Yuichi Terashima, Astrophysical Journal Letters, 806,   2015 06 20 , © 2015. The American Astronomical Society. All rights reserved.We present an unprecedented measurement of the disk stability and local instability scales in the luminous infrared Seyfert 1 host, NGC 7469, based on ALMA observations of dense gas tracers and with a synthesized beam of 165 × 132 pc. While we confirm that non-circular motions are not significant in redistributing the dense interstellar gas in this galaxy, we find compelling evidence that the dense gas is a suitable tracer for studying the origin of its intensely high-mass star-forming ringlike structure. Our derived disk stability parameter Q accounts for a thick disk structure, and its value falls below unity at the radii in which intense star formation is found. Furthermore, we derive the characteristic instability scale λc and find a striking agreement between our measured scale of ∼180 pc and the typical sizes of individual complexes of young and massive star clusters seen in high-resolution images.
  • Infrared and X-Ray evidence of an agn in the NGC 3256 southern nucleus
    Youichi Ohyama, Yuichi Terashima, Kazushi Sakamoto, Astrophysical Journal, 805,   2015 06 01 , © 2015. The American Astronomical Society. All rights reserved.We investigate signs of an active galactic nucleus (AGN) in the luminous infrared (IR) galaxy NGC 3256 at both IR and X-ray wavelengths. NGC 3256 has double nuclei: the northern and southern (hereafter, N and S nuclei, respectively). We show that the Spitzer IRAC colors extracted at the S nucleus are AGN-like, and the Spitzer IRS spectrum is bluer at <6 μm than at the N nucleus. We built for the S nucleus an AGN-starburst composite model with a heavily absorbed AGN to successfully reproduce not only the IRAC and IRS specrophotometries at ≃3″, but also the very deep silicate 9.7 μm absorption observed at a 0.″36 scale by Díaz-Santos et al. We found a 2.2 μm compact source at the S nucleus in an HST NICMOS image and identified its unresolved core (at 0.″ 26 resolution) with the compact core in previous mid-infrared observations at comparable resolution. The flux of the 2.2 μm core is consistent with our AGN spectral energy distribution model. We also analyzed a deeper than ever Chandra X-ray spectrum of the unresolved (at 0.″ 5 resolution) source at the S nucleus. We found that a dual-component power-law model (for primary and scattered ones) fits an apparently very hard spectrum with a moderately large absorption on the primary component. Together with a limit on equivalent width of a fluorescent Fe-K emission line at 6.4 keV, the X-ray spectrum is consistent with a typical Compton-thin Seyfert 2. We therefore suggest that the S nucleus hosts a heavily absorbed low-luminosity AGN.
  • Multimolecule ALMA observations toward the Seyfert 1 galaxy NGC 1097
    S. Martín, K. Kohno, K. Kohno, T. Izumi, M. Krips, D. S. Meier, D. S. Meier, R. Aladro, S. Matsushita, S. Takano, S. Takano, J. L. Turner, D. Espada, D. Espada, D. Espada, T. Nakajima, Y. Terashima, K. Fathi, K. Fathi, P. Y. Hsieh, P. Y. Hsieh, M. Imanishi, M. Imanishi, A. Lundgren, N. Nakai, E. Schinnerer, K. Sheth, T. Wiklind, Astronomy and Astrophysics, 573,   2015 01 01 , © ESO 2015.Context. The nearby Sy 1 galaxy NGC 1097 represents an ideal laboratory for exploring the molecular chemistry in the surroundings of an active galactic nucleus (AGN). Aims. Exploring the distribution of different molecular species allows us to understand the physical processes affecting the interstellar medium both in the AGN vicinity and in the outer star forming molecular ring. Methods. We carried out 3 mm ALMA observations that include seven different molecular species, namely HCN, HCO+, CCH, CS, HNCO, SiO, HC3N, and SO, as well as the 13C isotopologues of the first two. Spectra were extracted from selected positions and all species were imaged over the central 2 kpc (∼30″) of the galaxy at a resolution of ∼2.2″ × 1:5″ (150 pc × 100 pc). Results. HCO+ and CS appear to be slightly enhanced in the star forming ring. CCH shows the largest variations across NGC 1097 and is suggested to be a good tracer of both obscured and early stage star formation. HNCO, SiO, and HC3N are significantly enhanced in the inner circumnuclear disk surrounding the AGN. Conclusions. Differences in the molecular abundances are observed between the star forming ring and the inner circumnuclear disk. We conclude that the HCN/HCO+ and HCN/CS differences observed between AGN-dominated and starburst (SB) galaxies are not due to a HCN enhancement due to X-rays, but rather this enhancement is produced by shocked material at distances of 200 pc from the AGN. Additionally, we claim that lower HCN/CS is a combination of a small underabundance of CS in AGNs, together with excitation effects, where a high density gas component (∼106 cm-3) may be more prominent in SB galaxies. However, the most promising are the differences found among the dense gas tracers that, at our modest spatial resolution, seem to outline the physical structure of the molecular disk around the AGN. In this picture, HNCO probes the well-shielded gas in the disk, surrounding the dense material moderately exposed to the X-ray radiation traced by HC3N. Finally SiO might be the innermost molecule in the disk structure.
  • Hyper-luminous dust-obscured galaxies discovered by the Hyper Suprime-Cam on Subaru and WISE
    Yoshiki Toba, Tohru Nagao, Michael A. Strauss, Kentaro Aoki, Tomotsugu Goto, Masatoshi Imanishi, Masatoshi Imanishi, Masatoshi Imanishi, Toshihiro Kawaguchi, Yuichi Terashima, Yoshihiro Ueda, James Bosch, Kevin Bundy, Yoshiyuki Doi, Hanae Inami, Yutaka Komiyama, Yutaka Komiyama, Robert H. Lupton, Hideo Matsuhara, Hideo Matsuhara, Yoshiki Matsuoka, Satoshi Miyazaki, Satoshi Miyazaki, Tomoki Morokuma, Fumiaki Nakata, Nagisa Oi, Masafusa Onoue, Masafusa Onoue, Shinki Oyabu, Paul Price, Philip J. Tait, Tadafumi Takata, Tadafumi Takata, Manobu M. Tanaka, Tsuyoshi Terai, Edwin L. Turner, Edwin L. Turner, Tomohisa Uchida, Tomonori Usuda, Tomonori Usuda, Yousuke Utsumi, Yoshihiko Yamada, Shiang Yu Wang, Publications of the Astronomical Society of Japan, 67,   2015 01 01 , © The Author 2015. Published by Oxford University Press on behalf of the Astronomical Society of Japan.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.
  • Suzaku observation of IRAS 00521-7054, a peculiar type-II AGN with a very broad feature at 6 keV
    C. Ricci, F. Tazaki, F. Tazaki, Y. Ueda, S. Paltani, R. Boissay, Y. Terashima, Astrophysical Journal, 795,   2014 11 10 , © 2014. The American Astronomical Society. All rights reserved.IRAS 00521-7054 is the first Seyfert 2 in which the presence of an extremely large Fe Kα line has been claimed. We report here on the analysis of a 100 ks Suzaku observation of the source. We confirm the existence of a very strong excess over the power-law X-ray continuum at E ∼ 6 keV (EW ≃ 800 eV), extending down to ∼4.5 keV, and found that the X-ray spectrum of the source can be explained by two different models. (1) An absorption scenario in which the X-ray source is obscured by two fully covering ionized absorbers with a strong reflection component from neutral material (R ∼ 1.7), a blackbody component, and four narrow Gaussian lines (corresponding to Fe Kα, Fe Kβ, Fe XXV, and Fe XXVI). (2) A reflection scenario in which the X-ray spectrum is dominated by an obscured (log NH ∼ 22.9), blurred reflection produced in an ionized disk around a rotating supermassive black hole with a spin of a ≥ 0.73 and affected by light-bending (R ∼ 2.7), plus two narrow Gaussian lines (corresponding to Fe Kα and Fe Kβ). The narrow Fe Kα and Kβ lines are consistent with being produced by ionized iron and in particular by Fe XIV-Fe XVI and Fe XII-Fe XVI for the absorption and reflection scenario, respectively. While the X-ray continuum varies significantly during the observation, the intensity of the broad feature appears to be constant, in agreement with both the absorption and reflection scenarios. For both scenarios we obtained a steep power-law emission (Γ ∼ 2.2-2.3), and we speculate that the source might be an obscured narrow-line Seyfert 1.
  • Tracking the complex absorption in NGC 2110 with two Suzaku observations
    Elizabeth Rivers, Elizabeth Rivers, Alex Markowitz, Alex Markowitz, Richard Rothschild, Aya Bamba, Yasushi Fukazawa, Takashi Okajima, James Reeves, Yuichi Terashima, Yoshihiro Ueda, Astrophysical Journal, 786,   2014 05 10 , © 2014. The American Astronomical Society. All rights reserved.We present spectral analysis of two Suzaku observations of the Seyfert 2 galaxy, NGC 2110. This source has been known to show complex, variable absorption which we study in depth by analyzing these two observations set 7 yr apart and by comparing them to previously analyzed observations with the XMM-Newton and Chandra observatories. We find that there is a relatively stable, full-covering absorber with a column density of ∼3× 1022 cm-2, with an additional patchy absorber that is likely variable in both column density and covering fraction over timescales of years, consistent with clouds in a patchy torus or in the broad line region. We model a soft emission line complex, likely arising from ionized plasma and consistent with previous studies. We find no evidence for reflection from an accretion disk in this source with contribution from neither relativistically broadened Fe Kα line emission, nor from a Compton reflection hump.
  • The ASTRO-H X-ray astronomy satellite
    Tadayuki Takahashi, Kazuhisa Mitsuda, Richard Kelley, Felix Aharonian, Hiroki Akamatsu, Fumie Akimoto, Steve Allen, Naohisa Anabuki, Lorella Angelini, Keith Arnaud, Makoto Asai, Marc Audard, Hisamitsu Awaki, Philipp Azzarello, Chris Baluta, Aya Bamba, Nobutaka Bando, Marshall Bautz, Thomas Bialas, Roger D. Blandford, Kevin Boyce, Laura Brenneman, Gregory Brown, Ed Cackett, Edgar Canavan, Maria Chernyakova, Meng Chiao, Paolo Coppi, Elisa Costantini, Jelle De Plaa, Jan Willem Den Herder, Michael Dipirro, Chris Done, Tadayasu Dotani, John Doty, Ken Ebisawa, Teruaki Enoto, Yuichiro Ezoe, Andrew Fabian, Carlo Ferrigno, Adam Foster, Ryuichi Fujimoto, Yasushi Fukazawa, Stefan Funk, Akihiro Furuzawa, Massimiliano Galeazzi, Luigi Gallo, Poshak Gandhi, Kirk Gilmore, Matteo Guainazzi, Daniel Haas, Yoshito Haba, Kenji Hamaguchi, Atsushi Harayama, Isamu Hatsukade, Katsuhiro Hayashi, Takayuki Hayashi, Kiyoshi Hayashida, Junko Hiraga, Kazuyuki Hirose, Ann Hornschemeier, Akio Hoshino, John Hughes, Una Hwang, Ryo Iizuka, Yoshiyuki Inoue, Kazunori Ishibashi, Manabu Ishida, Kumi Ishikawa, Kosei Ishimura, Yoshitaka Ishisaki, Masayuki Itoh, Naoko Iwata, Naoko Iyomoto, Chris Jewell, Jelle Kaastra, Timothy Kallman, Tuneyoshi Kamae, Jun Kataoka, Satoru Katsuda, Junichiro Katsuta, Madoka Kawaharada, Nobuyuki Kawai, Taro Kawano, Shigeo Kawasaki, Dmitry Khangaluyan, Caroline Kilbourne, Mark Kimball, Masashi Kimura, Shunji Kitamoto, Tetsu Kitayama, Takayoshi Kohmura, Motohide Kokubun, Saori Konami, Tatsuro Kosaka, Alexander Koujelev, Katsuji Koyama, Hans Krimm, Aya Kubota, Hideyo Kunieda, Proceedings of SPIE - The International Society for Optical Engineering, 9144,   2014 01 01 , © 2014 SPIE.The joint JAXA/NASA ASTRO-H mission is the sixth in a series of highly successful X-ray missions developed by the Institute of Space and Astronautical Science (ISAS), with a planned launch in 2015. The ASTRO-H mission is equipped with a suite of sensitive instruments with the highest energy resolution ever achieved at E > 3 keV and a wide energy range spanning four decades in energy from soft X-rays to gamma-rays. The simultaneous broad band pass, coupled with the high spectral resolution of ΔE ≤ 7 eV of the micro-calorimeter, will enable a wide variety of important science themes to be pursued. ASTRO-H is expected to provide breakthrough results in scientific areas as diverse as the large-scale structure of the Universe and its evolution, the behavior of matter in the gravitational strong field regime, the physical conditions in sites of cosmic-ray acceleration, and the distribution of dark matter in galaxy clusters at different redshifts.
  • Reflection-dominated nuclear X-ray emission in the early-type galaxy ESO 565-G019
    P. Gandhi, P. Gandhi, Y. Terashima, S. Yamada, R. F. Mushotzky, Y. Ueda, W. H. Baumgartner, D. M. Alexander, J. Malzac, J. Malzac, K. Vaghmare, T. Takahashi, T. Takahashi, C. Done, Astrophysical Journal, 773,   2013 08 10 , We present the discovery of a reflection-dominated active galactic nucleus (AGN) in the early-type radio-quiet galaxy ESO 565-G019 with Suzaku and Swift/Burst Alert Telescope. The source X-ray spectrum below 10 keV is characteristic of other Compton-thick (CT) AGNs, clearly showing an inverted continuum and prodigious fluorescence iron emission above ∼3 keV. A Compton shoulder to the neutral Fe Kα line also appears to be present. There is evidence for long-term hard X-ray flux variability that we associate with changes in the intrinsic AGN power law. More of such reflection-dominated AGNs should be uncovered in the near future with the increased sensitivity of ongoing and new hard X-ray surveys. ESO 565-G019 is hosted in an early-type galaxy whose morphology has been variously classified as either type E or type S0. Only about 20 bona fide CT-AGNs have been identified in the local universe so far, and all exist in host galaxies with late Hubble types (S0 or later). CT columns of nuclear obscuring gas are uncommon in early-type galaxies in the local universe, so confirmation of the exact morphological class of ESO 565-G019 is important. Infrared photometry also shows the presence of large quantities of cool dust in the host, indicative of significant ongoing star formation. ESO 565-G019 may be the first identified local example of minor-merger-driven CT-AGN growth in an early-type host, or may be the result of interaction with its neighboring galaxy ESO 565-G018 in a wide pair. © 2013. The American Astronomical Society. All rights reserved.
  • Suzaku view of the swift/bat active galactic nuclei. V. torus structure of two luminous radio-loud active galactic nuclei (3C 206 and PKS 0707-35)
    Fumie Tazaki, Yoshihiro Ueda, Yuichi Terashima, Richard F. Mushotzky, Francesco Tombesi, Francesco Tombesi, Astrophysical Journal, 772,   2013 07 20 , We present the results from broadband X-ray spectral analysis of 3C 206 and PKS 0707-35 with Suzaku and Swift/BAT, two of the most luminous unobscured and obscured radio-loud active galactic nuclei (AGNs) with hard X-ray luminosities of 1045.5 erg s-1 and 1044.9 erg s-1 (14-195 keV), respectively. Based on the radio core luminosity, we estimate that the X-ray spectrum of 3C 206 contains a significant (60% in the 14-195 keV band) contribution from the jet, while it is negligible in PKS 0707-35. We can successfully model the spectra with the jet component (for 3C 206), the transmitted emission, and two reflection components from the torus and the accretion disk. The reflection strengths from the torus are found to be R torus(≡ Ω/2π) = 0.29 ± 0.18 and 0.41 ± 0.18 for 3C 206 and PKS 0707-35, respectively, which are smaller than those in typical Seyfert galaxies. Utilizing the torus model by Ikeda et al., we quantify the relation between the half-opening angle of a torus (oa) and the equivalent width of an iron-K line. The observed equivalent width of 3C 206, < 71 eV, constrains the column density in the equatorial plane to <10 23 cm-2, or the half-opening angle to oa > 80° if =1024 cm-2 is assumed. That of PKS 0707-35, 72 ± 36 eV, is consistent with 1023 cm-2. Our results suggest that the tori in luminous radio-loud AGNs are only poorly developed. The trend is similar to that seen in radio-quiet AGNs, implying that the torus structure is not different between AGNs with jets and without jets. © 2013. The American Astronomical Society. All rights reserved.
  • Broadband X-ray spectra of two low-luminosity active galactic nuclei NGC 1566 and NGC 4941 observed with Suzaku
    Taiki Kawamuro, Yoshihiro Ueda, Fumie Tazaki, Yuichi Terashima, Astrophysical Journal, 770,   2013 06 20 , We report the first broadband X-ray spectra of the low-luminosity active galactic nuclei (LLAGNs), NGC 1566 (type 1.5) and NGC 4941 (type 2), observed with Suzaku and Swift/BAT covering the 0.5-195 keV band. Both targets have hard X-ray luminosities of ∼1041-42 erg s-1 in the 15-55 keV band. The spectra of the nucleus are well reproduced by a sum of partially or fully covered transmitted emission and its reflection from the accretion disk, reprocessed emission from the torus accompanied by a strong narrow iron-Kα line, and a scattered component (for NGC 4941). We do not significantly detect a broad iron-Kα line from the inner accretion disk in both targets, and obtain an upper limit on the corresponding solid angle of Ω/2π < 0.3 in NGC 1566. The reflection strength from the torus is moderate, in NGC 1566 and in NGC 4941. Comparison of the equivalent width of the narrow iron-Kα line with a model prediction based on a simple torus geometry constrains its half-opening angle to be θoa ≃ 60°-70° in NGC 4941. These results agree with the obscured AGN fraction obtained from hard X-ray and mid-infrared selected samples at similar luminosities. Our results support the implication that the averaged covering fraction of AGN tori is peaked at L ∼ 1042-43 erg s-1 but decreases toward lower luminosities. © 2013. The American Astronomical Society. All rights reserved..
  • The ASTRO-H X-ray observatory
    Tadayuki Takahashi, Kazuhisa Mitsuda, Richard Kelley, Henri Aarts, Felix Aharonian, Hiroki Akamatsu, Fumie Akimotoe, Steve Allen, Naohisa Anabuki, Lorella Angelini, Keith Arnaud, Makoto Asai, Marc Audard, Hisamitsu Awaki, Philipp Azzarello, Chris Baluta, Aya Bamba, Nobutaka Bando, Mark Bautz, Roger Blandford, Kevin Boyce, Greg Brown, Ed Cackett, Maria Chernyakova, Paolo Coppi, Elisa Costantini, Jelle De Plaa, Jan Willem Den Herder, Michael DiPirro, Chris Done, Tadayasu Dotani, John Doty, Ken Ebisawa, Megan Eckart, Teruaki Enoto, Yuichiro Ezoe, Andrew Fabian, Carlo Ferrigno, Adam Foster, Ryuichi Fujimoto, Yasushi Fukazawa, Stefan Funk, Akihiro Furuzawa, Massimiliano Galeazzi, Luigi Gallo, Poshak Gandhi, Keith Gendreau, Kirk Gilmore, Daniel Haas, Yoshito Haba, Kenji Hamaguchi, Isamu Hatsukade, Takayuki Hayashi, Kiyoshi Hayashida, Junko Hiraga, Kazuyuki Hirose, Ann Hornschemeier, Akio Hoshino, John Hughes, Una Hwang, Ryo Iizuka, Yoshiyuki Inoue, Kazunori Ishibashi, Manabu Ishida, Kosei Ishimura, Yoshitaka Ishisaki, Masayuki Ito, Naoko Iwat, Naoko Iyomoto, Jelle Kaastr, Timothy Kallman, Tuneyoshi Kamae, Jun Kataoka, Satoru Katsuda, Hajime Kawahara, Madoka Kawaharada, Nobuyuki Kawai, Shigeo Kawasaki, Dmitry Khangaluyan, Caroline Kilbourne, Masashi Kimura, Kenzo Kinugasaa, Shunji Kitamoto, Tetsu Kitayama, Takayoshi Kohmura, Motohide Kokubun, Tatsuro Kosaka, Alex Koujelev, Katsuji Koyama, Hans Krimm, Aya Kubota, Hideyo Kunieda, Stephanie LaMass, Philippe Laurent, Francois Lebrun, Maurice Leutenegger, Olivier Limousin, Michael Loewenstein, Knox Long, David Lumb, Proceedings of SPIE - The International Society for Optical Engineering, 8443,   2012 12 01 , The joint JAXA/NASA ASTRO-H mission is the sixth in a series of highly successful X-ray missions initiated by the Institute of Space and Astronautical Science (ISAS). ASTRO-H will investigate the physics of the highenergy universe via a suite of four instruments, covering a very wide energy range, from 0.3 keV to 600 keV. These instruments include a high-resolution, high-Throughput spectrometer sensitive over 0.3-12 keV with high spectral resolution of ?E 5 7 eV, enabled by a micro-calorimeter array located in the focal plane of thin-foil X-ray optics; hard X-ray imaging spectrometers covering 5-80 keV, located in the focal plane of multilayer-coated, focusing hard X-ray mirrors; a wide-field imaging spectrometer sensitive over 0.4-12 keV, with an X-ray CCD camera in the focal plane of a soft X-ray telescope; and a non-focusing Compton-camera type soft gamma-ray detector, sensitive in the 40-600 keV band. The simultaneous broad bandpass, coupled with high spectral resolution, will enable the pursuit of a wide variety of important science themes. © 2012 SPIE.
  • The low-mass, highly accreting black hole associated with the active galactic nucleus 2XMM J123103.2+110648
    Luis C. Ho, Minjin Kim, Minjin Kim, Yuichi Terashima, Astrophysical Journal Letters, 759,   2012 11 01 , Optical spectra and images taken with the Baade 6.5m Magellan telescope confirm that 2XMM J123103.2+110648, a highly variable X-ray source with an unusually soft spectrum, is indeed associated with a type 2 (narrow-line) active nucleus at a redshift of z = 0.11871. The absence of broad Hα or Hβ emission in an otherwise X-ray unabsorbed source suggests that it intrinsically lacks a broad-line region. If, as in other active galaxies, the ionized gas and stars in J1231+1106 are in approximate virial equilibrium, and the M BH - σ* relation holds, the exceptionally small velocity dispersion of σ = 33.5kms-1 for [O III] λ5007 implies that M BH ≈ 105 M ⊙, among the lowest ever detected. Such a low black hole mass is consistent with the general characteristics of the host, a small, low-luminosity, low-mass disk galaxy. We estimate the Eddington ratio of the black hole to be ≳0.5, in good agreement with expectations based on the X-ray properties of the source. © 2012. The American Astronomical Society. All rights reserved.
  • Mid- and far-infrared properties of a complete sample of local active galactic nuclei
    Kohei Ichikawa, Yoshihiro Ueda, Yuichi Terashima, Shinki Oyabu, Poshak Gandhi, Keiko Matsuta, Takao Nakagawa, Astrophysical Journal, 754,   2012 07 20 , 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 (14-195keV) 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. © 2012. The American Astronomical Society. All rights reserved.
  • Infrared and hard X-ray diagnostics of active galactic nucleus identification from the Swift/bat and AKARI all-sky surveys
    K. Matsuta, K. Matsuta, P. Gandhi, T. Dotani, T. Dotani, T. Nakagawa, N. Isobe, Y. Ueda, K. Ichikawa, Y. Terashima, S. Oyabu, I. Yamamura, I. Yamamura, Stawarz, Stawarz, Astrophysical Journal, 753,   2012 07 10 , We combine data from two all-sky surveys in order to study the connection between the infrared and hard X-ray (>10keV) 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 22month 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 (14-195keV) 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. © 2012. The American Astronomical Society. All rights reserved..
  • Hubble Space Telescope Identification of the Optical Counterparts of Ultraluminous X-ray Sources in M51
    Astrophysical Journal, 645,   2006
  • The X-Ray Observatory Suzaku
    Publications of the Astronomical Society of Japan, 59,   2007
  • Suzaku Observation of Two Ultraluminous X-Ray Sources in NGC 1313
    Publications of the Astronomical Society of Japan, 59,   2007
  • Precision Fe Kα and Fe Kβ Line Spectroscopy of the Seyfert 1.9 Galaxy NGC 2992 with Suzaku
    Publications of the Astronomical Society of Japan, 59,   2007
  • Revealing the High Energy Emission from the Obscured Seyfert Galaxy MCG-5-23-16 with Suzaku
    Publications of the Astronomical Society of Japan, 59,   2007
  • Suzaku Observations of the Hard X-Ray Variability of MCG -6-30-15: the Effects of Strong Gravity around a Kerr Black Hole
    Publications of the Astronomical Society of Japan, 59,   2007
  • Radiatively Inefficient Accretion Flow in the Nucleus of NGC 1097
    Astrophysical Journal, 643,   2006
  • A Search for X-Rays from the Long-Duration Microlensing Event MACHO-96-BLG-5
    Astrophysical Journal, 631,   2005
  • Deconstructing NGC 7130
    Astrophysical Journal, 618,   2005
  • Testing Radiatively Inefficient Accretion Flow Theory: An XMM-Newton Observation of NGC 3998
    Astrophysical Journal, 606,   2004
  • Accretion and Outflow in the Active Galactic Nucleus and Starburst of NGC 5135
    Astrophysical Journal, 602,   2004
  • The Luminous X-Ray Source Population in M51 Observed with Chandra
    Astrophysical Journal, 601,   2004
  • X-ray-Underluminous Active Galactic Nuclei Relative to Broad Emission Lines in Ultraluminous Infrared Galaxies
    Astronomical Journal, 127,   2004
  • X-Ray-Extreme-Ultraviolet Simultaneous Observations of NGC 5548: Fast Extreme-Ultraviolet Dip without X-Ray Variation
    Astrophysical Journal, 599,   2003
  • X-Ray Evidence of a Buried Active Galactic Nucleus in UGC 5101
    Astrophysical Journal, 596,   2003
  • Detection of the ``Active'' Nucleus of M32
    Astrophysical Journal, 589,   2003
  • A Stringent Limit on the Accretion Luminosity of the Possible Central Black Hole in the Globular Cluster M15
    Astrophysical Journal, 587,   2003
  • Chandra Snapshot Observations of Low-Luminosity Active Galactic Nuclei with a Compact Radio Source
    Astrophysical Journal, 583,   2003
  • Extreme X-Ray Iron Lines in Active Galactic Nuclei
    Astrophysical Journal, 573,   2002
  • X-Ray Emission from the Type Ic Supernova 1994I Observed with Chandra
    Astrophysical Journal, 573,   2002
  • X-Ray Properties of LINERs and Low-Luminosity Seyfert Galaxies Observed with ASCA. I. Observations and Results
    Astrophysical Journal Supplement Series, 139,   2002
  • A Chandra X-Ray Study of Cygnus A. III. The Cluster of Galaxies
    Astrophysical Journal, 565,   2002
  • A Chandra X-Ray Study of Cygnus A. II. The Nucleus
    Astrophysical Journal, 564,   2002
  • A Chandra Observation of M51: Active Nucleus and Nuclear Outflows
    Astrophysical Journal, 560,   2001
  • Estimation of Central Black Hole Masses in Low-Luminosity Active Galactic Nuclei
    Publications of the Astronomical Society of Japan, 53,   2001
  • RXTE observation of NGC 6240: a search for the obscured active nucleus
    Monthly Notices of the Royal Astronomical Society, 316,   2000
  • Hard X-Ray Emission and the Ionizing Source in LINERs
    Astrophysical Journal, 539,   2000
  • Iron K Line Variability in the Low-Luminosity Active Galactic Nucleus NGC 4579
    Astrophysical Journal, 535,   2000
  • ASCA Observations of ``Type 2'' LINERs: Evidence for a Stellar Source of Ionization
    Astrophysical Journal, 533,   2000
  • X-Ray Properties of the Weak Seyfert 1 Nucleus in NGC 4639
    Astrophysical Journal, 525,   1999
  • ASCA Observation of the Low-Luminosity Seyfert 1.5 Galaxy NGC 5033
    Publications of the Astronomical Society of Japan, 1,   1999
  • Detection of an Iron K Emission Line from the LINER NGC 4579
    Astrophysical Journal, 503,   1998
  • Detection of an X-ray periodicity in the Seyfert galaxy IRAS 18325-5926
    Monthly Notices of the Royal Astronomical Society, 295,   1998
  • An ASCA Observation of M51 (NGC 5194): Iron K Emission from an Obscured Active Galactic Nucleus
    Astrophysical Journal, 496,   1998
  • The New AM Herculis--Type Object AX J2315-592 Discovered with ASCA
    Astrophysical Journal, 470,   1996
  • X-Ray Properties of the Nucleus of M81
    Publications of the Astronomical Society of Japan, 48,   1996
  • The Nature of the Low-Luminosity Active Galactic Nuclei in NGC 3147
    Astrophysical Journal, 459,   1996
  • The Hard X-Ray Emission of NGC 3628 and the Contribution of Low-Luminosity Spiral Galaxies to the Cosmic X-Ray Background
    Astrophysical Journal, 455,   1995
  • X-ray spectra of two quasars at z~1
    Monthly Notices of the Royal Astronomical Society, 276,   1995
  • Fe K emission from the hidden quasar IRAS P09104+4109
    Astrophysical Journal, 436,   1994
  • The complex X-ray spectra of two high redshift quasars observed with ASCA
    Publications of the Astronomical Society of Japan, 46,   1994
  • Probing the Disk-jet Connection of the Radio Galaxy 3C 120 Observed with Suzaku
    Publications of the Astronomical Society of Japan, 59,   2007
  • Fe K Line Profile in Low-redshift Quasars: Average Shape and Eddington Ratio Dependence
    Astrophysical Journal, 662,   2007
  • Suzaku observations of iron lines and reflection in AGN
    Astronomische Nachrichten, 327,   2006
  • Monitoring the Violent Activity from the Inner Accretion Disk of the Seyfert 1.9 Galaxy NGC 2992 with RXTE
    666,   2007
  • Suzaku Observations of Active Galactic Nuclei Detected in the Swift/BAT Survey: Discovery of "New Type'' of Buried Supermassive Black Holes
    Astrophysical Journal, 664,   2007
  • Detailed hard X-ray measurements of the nuclear emission from the Seyfert 2 galaxy NGC 4388 with Suzaku
    Publications of the Astronomical Society of Japan, 60,   2008
  • Wide-band spectroscopy of the Compton-thick Seyfert 2 galaxy Mrk 3 with Suzaku
    Publications of the Astronomical Society of Japan, 60,   2008
  • Outflow-dominated Emission from the Quiescent Massive Black Holes in NGC 4621 and NGC 4697
    675,   2008
  • On why the Iron K-shell absorption in AGN is not a signature of the local Warm/Hot Intergalactic Medium
    Monthly Notices of the Royal Astronomical Society Letters, 385,   2008
  • Implication for the Super-Critical Accretion Flow in the Narrow-Line Seyfert 1 Galaxy PKS 0558-504
    Publications of the Astronomical Society of Japan, 61,   2008
  • Suzaku Observations of Local Ultraluminous Infrared Galaxies
    Astrophysical Journal, 691,   2009
  • Suzaku Observations of the Circinus Galaxy
    Astrophysical Journal, 691,   2009
  • Study on X-ray Spectra of Obscured AGNs based on Monte Carlo Simulation - An Interpretation of Observed Wide-band Spectra
    Astrophysical Journal, 692,   2009
  • Detection of Hard X-Rays from the Compton-thick Seyfert 2 Galaxy NGC 2273 with Suzaku
    Publications of the Astronomical Society of Japan, 61,   2009
  • X-Ray Spectral Variability of the Seyfert Galaxy NGC 4051 Observed with Suzaku
    Publications of the Astronomical Society of Japan, 61,   2009
  • Suzaku View of the Swift/BAT Active Galactic Nuclei (I): Spectral Analysis of SixAGNs and Evidence for Two Types of Obscured Population
    Astrophysical Journal, 696,   2009
  • Suzaku View of the Swift/BAT Active Galactic Nuclei (II): Time Variability and Spectra of Five ``Hidden'' AGNs
    Astrophysical Journal, 701,   2009
  • A New Sample of Buried AGN Selected from the Second XMM-Newton Serendipitous Source Catalogue
    Astrophysical Journal, 806,   2009
  • Spectral Variation of the Seyfert 1 Galaxy MCG-6-30-15 observed with Suzaku
    Publications of the Astronomical Society of Japan, 61,   2009
  • Scattered X-rays in Obscured Active Galactic Nuclei and their Implications for Geometrical Structure and Evolution
    Astrophysical Journal, 711, (1,Pt.1) 144 - 156,   2010
  • Suzaku Observation of the Brightest Broad-Line Radio Galaxy 4C 50.55 (IGR J 21247+5058)
    Astrophysical Journal, 721, (2,Pt.1) 1340 - 1347,   2010
  • Iron line profiles in Suzaku spectra of bare Seyfert galaxies
    Monthly Notices of the Royal Astronomical Society, 411, (4) 2353 - 2370,   2011
  • Suzaku View of the Swift/BAT Active Galactic Nuclei. III. Application of Numerical Torus Models to Two Nearly Compton Thick AGNs (NGC 612 and NGC 3081)
    Astrophysical Journal, 721,   2011
  • Suzaku View of the Swift/BAT Active Galactic Nuclei. IV. Nature of Two Narrow-line Radio Galaxies (3C 403 and IC 5063)
    in press,   2011


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