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Nature of hard X-ray (3-24 keV) detected luminous infrared galaxies in the COSMOS field

Matsuoka, Kenta and Ueda, Yoshihiro (2017) Nature of hard X-ray (3-24 keV) detected luminous infrared galaxies in the COSMOS field. Astrophysical Journal, 838 (2). Art. No. 128. ISSN 1538-4357.

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We investigate the nature of far-infrared (70 μm) and hard X-ray (3–24 keV) selected galaxies in the COSMOS field detected with both Spitzer and the Nuclear Spectroscopic Telescope Array (NuSTAR). By matching the Spitzer-COSMOS catalog with the NuSTAR-COSMOS catalog, we obtain a sample consisting of a hyperluminous infrared galaxy with log(L_(IR)/L⊙) ⩾ 13, 12 ultraluminous infrared galaxies with 12 ⩽ log (L_(IR)/L⊙) ⩽ 13, and 10 luminous infrared galaxies with 11⩽ log (L_(IR)/L⊙ ⩽ 12, i.e., 23 Hy/U/LIRGs in total. Using their X-ray hardness ratios, we find that 12 sources are obscured active galactic nuclei (AGNs) with absorption column densities of N_H > 10^(22) cm^(−2), including several Compton-thick (N_H ~ 10^(24) cm^(−2)) AGN candidates. On the basis of the infrared (60 μm) and intrinsic X-ray luminosities, we examine the relation between star formation (SF) and AGN luminosities of the 23 Hy/U/LIRGs. We find that the correlation is similar to that of the optically selected AGNs reported by Netzer, whereas local, far-infrared selected U/LIRGs show higher SF-to-AGN luminosity ratios than the average of our sample. This result suggests that our Hy/U/LIRGs detected both with Spitzer and NuSTAR are likely situated in a transition epoch between AGN-rising and cold-gas diminishing phases in SF-AGN evolutional sequences. The nature of a Compton-thick AGN candidate newly detected above 8 keV with NuSTAR (ID 245 in Civano et al.) is briefly discussed.

Item Type:Article
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URLURL TypeDescription Paper
Matsuoka, Kenta0000-0002-2689-4634
Ueda, Yoshihiro0000-0001-7821-6715
Additional Information:© 2017 The American Astronomical Society. Received 2016 July 27; revised 2017 February 9; accepted 2017 February 28; published 2017 April 3. We would like to thank Taiki Kawamuro, Atsushi Tanimoto, Kohei Ichikawa, and Tohru Nagao for helpful comments and suggestions, and Takamitsu Miyaji for his help on the energy responses of Chandra and XMM-Newton. We also thank the anonymous referee for useful comments and suggestions. This work was financially supported by the Japan Society for the Promotion of Science (JSPS) KAKENHI Grant No. 14J01811 (K.M.) and 26400228 (Y.U.).
Subject Keywords:galaxies: active – galaxies: evolution – infrared: galaxies
Issue or Number:2
Record Number:CaltechAUTHORS:20170310-092959543
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Official Citation:Kenta Matsuoka and Yoshihiro Ueda 2017 ApJ 838 128
Usage Policy:No commercial reproduction, distribution, display or performance rights in this work are provided.
ID Code:75018
Deposited By: Joy Painter
Deposited On:10 Mar 2017 19:16
Last Modified:03 Oct 2019 16:45

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