TY - JOUR
T1 - Role of active galactic nuclei in the luminous infrared galaxy phase at z ≤ 3
AU - Lin, Ming Yi
AU - Hashimoto, Yasuhiro
AU - Foucaud, Sébastien
N1 - Funding Information:
We would like to appreciate the anonymous referee for his/her patience and constructive suggestions and corrections that further improved this paper. We also thank Richard Davies for correcting the English text in the manuscript. The work presented here is supported by the National Science Council of Taiwan under the grants NSC99-2112-M-003-002-MY2, NSC99-2119-M-003-005, and NSC99-2112-M-003-001-MY2. We would like to acknowledge the wonderful work done by Jeyhan S. Kartaltepe on the S-COSMOS 70 µm point-source catalogue, on which our analyses are based. We would like to thank the following people for very useful discussions, suggestions, and comments: Lin-Wen Chen, Jeyhan S. Kartaltepe, Wei-Hao Wang, Albert Kong, Matthew A. Malkan, Nick Scoville, David B. Sanders, Richard Davies, David Rosario, and Dieter Lutz. This research extensively used the COSMOS survey archive data of the NASA/IPAC Infrared Science Archive, which is operated by the Jet Propulsion Laboratory, California Institute of Technology, under contract with the National Aeronautics and Space Administration.
Publisher Copyright:
© 2015 The Authors.
PY - 2016/3/1
Y1 - 2016/3/1
N2 - To understand the interactions between active galactic nuclei (AGNs) and star formation during the evolution of galaxies, we investigate 142 galaxies detected in both X-ray and 70 μm observations in the COSMOS (Cosmic Evolution Survey) field. All of our data are obtained from the archive X-ray point-source catalogues from Chandra andXMM-Newton observations, and the far-infrared 70 μm point-source catalogue from Spitzer-MIPS observations. Although the IRAC [3.6 μm]-[4.5 μm] versus [5.8 μm]-[8.0 μm] colours of our sample indicate that only ~63 per cent of our sources would be classified as AGNs, the ratio of the rest-frame 2-10 keV luminosity to the total infrared luminosity (8-1000 μm) shows that the entire sample has comparatively higher X-ray luminosity than that expected from pure star-forming galaxies, suggesting the presence of an AGN in all of our sources. From an analysis of the X-ray hardness ratio, we find that sources with both 70 μm and X-ray detection tend to have a higher hardness ratio relative to the whole X-ray-selected source population, suggesting the presence of more X-ray absorption in the 70 μm detected sources. In addition, we find that the observed far-infrared colours of 70 μm detected sources with and without X-ray emission are similar, suggesting the far-infrared emission could be mainly powered by star formation.
AB - To understand the interactions between active galactic nuclei (AGNs) and star formation during the evolution of galaxies, we investigate 142 galaxies detected in both X-ray and 70 μm observations in the COSMOS (Cosmic Evolution Survey) field. All of our data are obtained from the archive X-ray point-source catalogues from Chandra andXMM-Newton observations, and the far-infrared 70 μm point-source catalogue from Spitzer-MIPS observations. Although the IRAC [3.6 μm]-[4.5 μm] versus [5.8 μm]-[8.0 μm] colours of our sample indicate that only ~63 per cent of our sources would be classified as AGNs, the ratio of the rest-frame 2-10 keV luminosity to the total infrared luminosity (8-1000 μm) shows that the entire sample has comparatively higher X-ray luminosity than that expected from pure star-forming galaxies, suggesting the presence of an AGN in all of our sources. From an analysis of the X-ray hardness ratio, we find that sources with both 70 μm and X-ray detection tend to have a higher hardness ratio relative to the whole X-ray-selected source population, suggesting the presence of more X-ray absorption in the 70 μm detected sources. In addition, we find that the observed far-infrared colours of 70 μm detected sources with and without X-ray emission are similar, suggesting the far-infrared emission could be mainly powered by star formation.
KW - Galaxies: active
KW - Galaxies: high-redshift
KW - Infrared: galaxies
KW - X-rays: galaxies
UR - http://www.scopus.com/inward/record.url?scp=84964426948&partnerID=8YFLogxK
UR - http://www.scopus.com/inward/citedby.url?scp=84964426948&partnerID=8YFLogxK
U2 - 10.1093/mnras/stv2766
DO - 10.1093/mnras/stv2766
M3 - Article
AN - SCOPUS:84964426948
SN - 0035-8711
VL - 456
SP - 2735
EP - 2748
JO - Monthly Notices of the Royal Astronomical Society
JF - Monthly Notices of the Royal Astronomical Society
IS - 3
ER -