@article{98411a6ac7d74448ac0f619988651aa8,
title = "X-ray constraints on the fraction of obscured active galactic nuclei at high accretion luminosities",
abstract = "The wide-area XMM-XXL X-ray survey is used to explore the fraction of obscured active galactic nuclei (AGNs) at high accretion luminosities, LX(2-10 keV) ≳ 1044 erg s-1, and out to redshift z ≈ 1.5. The sample covers an area of about 14 deg2 and provides constraints on the space density of powerful AGNs over a wide range of neutral hydrogen column densities extending beyond the Compton-thick limit, NH ≈ 1024 cm-2. The fraction of obscured Compton-thin (NH = 1022-1024 cm-2) AGNs is estimated to be ≈0.35 for luminosities LX(2-10 keV) > 1044 erg s-1, independent of redshift. For less luminous sources, the fraction of obscured Compton-thin AGNs increases from 0.45 ± 0.10 at z = 0.25 to 0.75 ± 0.05 at z = 1.25. Studies that select AGNs in the infrared via template fits to the observed spectral energy distribution of extragalactic sources estimate space densities at high accretion luminosities consistent with the XMM-XXL constraints. There is no evidence for a large population of AGNs (e.g. heavily obscured) identified in the infrared and missed at X-ray wavelengths. We further explore the mid-infrared colours of XMM-XXL AGNs as a function of accretion luminosity, column density and redshift. The fraction of XMM-XXL sources that lie within the mid-infrared colour wedges defined in the literature to select AGNs is primarily a function of redshift. This fraction increases from about 20-30 per cent at z = 0.25 to about 50-70 per cent at z = 1.5.",
author = "A. Georgakakis and M. Salvato and Z. Liu and J. Buchner and Brandt, {W. N.} and {Tasnim Ananna}, T. and A. Schulze and Yue Shen and S. LaMassa and K. Nandra and A. Merloni and McGreer, {I. D.}",
note = "Funding Information: We thank the anonymous referee for useful comments and suggestions. This work benefited from the THALES project 383549, which is jointly funded by the European Union and the Greek Government in the framework of the programme {\textquoteleft}Education and lifelong learning{\textquoteright}. We acknowledge support from the FONDECYT Postdoctorados 3160439 (JB) and the Ministry of Economy, Development, and Tourism{\textquoteright}s Millennium Science Initiative through grant IC120009, awarded to The Millennium Institute of Astro- physics MAS (JB). Funding for SDSS-III has been provided by the Alfred P. Sloan Foundation, the Participating Institutions, the National Science Foundation and the U.S. Department of Energy Office of Science. The SDSS-III website is http://www.sdss3.org/. SDSS-III is managed by the Astrophysical Research Consortium for the Participating Institutions of the SDSS-III Collaboration including the University of Arizona, the Brazilian Participation Group, Brookhaven National Laboratory, Carnegie Mellon University, University of Florida, the French Participation Group, the German Participation Group, Harvard University, the Instituto de Astrofisica de Canarias, the Michigan State/Notre Dame/JINA Participation Group, Johns Hopkins University, Lawrence Berkeley National Laboratory, Max Planck Institute for Astrophysics, Max Planck Institute for Extraterrestrial Physics, New Mexico State University, New York University, Ohio State University, Pennsylvania State University, University of Portsmouth, Princeton University, the Spanish Participation Group, University of Tokyo, University of Utah, Vanderbilt University, University of Virginia, University of Washington and Yale University. Funding Information: We thank the anonymous referee for useful comments and suggestions. This work benefited from the THALES project 383549, which is jointly funded by the European Union and the Greek Government in the framework of the programme 'Education and lifelong learning'. We acknowledge support from the FONDECYT Postdoctorados 3160439 (JB) and the Ministry of Economy, Development, and Tourism's Millennium Science Initiative through grant IC120009, awarded to The Millennium Institute of Astrophysics MAS (JB). Funding for SDSS-III has been provided by the Alfred P. Sloan Foundation, the Participating Institutions, the National Science Foundation and the U.S. Department of Energy Office of Science. The SDSS-III website is http://www.sdss3.org/. SDSS-III is managed by the Astrophysical Research Consortium for the Participating Institutions of the SDSS-III Collaboration including the University of Arizona, the Brazilian Participation Group, Brookhaven National Laboratory, Carnegie Mellon University, University of Florida, the French Participation Group, the German Participation Group, Harvard University, the Instituto de Astrofisica de Canarias, the Michigan State/Notre Dame/JINA Participation Group, Johns Hopkins University, Lawrence Berkeley National Laboratory, Max Planck Institute for Astrophysics, Max Planck Institute for Extraterrestrial Physics, NewMexico State University, New York University, Ohio State University, Pennsylvania State University, University of Portsmouth, Princeton University, the Spanish Participation Group, University of Tokyo, University of Utah, Vanderbilt University, University of Virginia, University of Washington and Yale University. Publisher Copyright: {\textcopyright} 2017 The Authors.",
year = "2017",
month = aug,
day = "11",
doi = "10.1093/mnras/stx953",
language = "English (US)",
volume = "469",
pages = "3232--3251",
journal = "Monthly Notices of the Royal Astronomical Society",
issn = "0035-8711",
publisher = "Oxford University Press",
number = "3",
}