@article{146da788bf784857b827f0408f81ee02,
title = "Observational constraints on the specific accretion-rate distribution of X-ray-selected AGNs",
abstract = "This paper estimates the specific accretion-rate distribution of AGNs using a sample of 4821 X-ray sources from both deep and shallow surveys. The specific accretion-rate distribution is used as a proxy of the Eddington ratio and is defined as the probability of a galaxy with a given stellarmass and redshift hosting an active nucleus with a certain specific accretion rate. We find that the probability of a galaxy hosting an AGN increases with decreasing specific accretion rate. There is evidence that this trend reverses at low specific accretion rates, λ ≲ 10-4-10-3 (Eddington units). There is a break close to the Eddington limit, above which the probability of an accretion event decreases steeply. The specific accretion-rate distribution evolves such that the fraction of AGNs among galaxies drops towards lower redshifts. This decrease in the AGN duty cycle is responsible for the strong evolution of the accretion density of the Universe from redshift z ≈ 1-1.5 to the present day. Our analysis also suggests that this evolution is accompanied by a decoupling of accretion events on to black holes from the formation of stars in galaxies. There is also evidence that at earlier times the relative probability of high versus low specific accretion-rate events among galaxies increases. We argue that this differential redshift evolution of the AGN duty cycle with respect to λ produces the AGN downsizing trend, whereby luminous sources peak at earlier epochs compared to less luminous ones. Finally, we also find a stellar mass dependence of the specific accretion-rate distribution, with more massive galaxies avoiding high specific accretion-rate events.",
author = "A. Georgakakis and J. Aird and A. Schulze and T. Dwelly and M. Salvato and K. Nandra and A. Merloni and Schneider, {D. P.}",
note = "Funding Information: The authors thank the anonymous referee for their careful reading of the paper and their constructive comments. This work benefited from the THALES project 383549 that is jointly funded by the European Union and the Greek Government in the framework of the programme 'Education and lifelong learning'. JA acknowledges support from ERC Advanced Grant FEEDBACK 340442. AS acknowledges support by JSPS KAKENHI Grant Number 26800098. Funding for the Sloan Digital Sky Survey IV has been provided by the Alfred P. Sloan Foundation, the U.S. Department of Energy Office of Science and the Participating Institutions. SDSS acknowledges support and resources from the Center for High-Performance Computing at the University of Utah. The SDSS web site is www.sdss.org. SDSS is managed by the Astrophysical Research Consortium for the Participating Institutions of the SDSS Collaboration including the Brazilian Participation Group, the Carnegie Institution for Science, Carnegie Mellon University, the Chilean Participation Group, the French Participation Group, Harvard-Smithsonian Center for Astrophysics, Instituto de Astrof {\'i}sica de Canarias, The Johns Hopkins University, Kavli Institute for the Physics and Mathematics of the Universe (IPMU)/University of Tokyo, Lawrence Berkeley National Laboratory, Leibniz Institut f{\"u}r Astrophysik Potsdam (AIP), Max-Planck-Institut f{\"u}r Astronomie (MPIA Heidelberg), Max-Planck-Institut f{\"u}r Astrophysik (MPA Garching), Max-Planck-Institut f{\"u}r Extraterrestrische Physik (MPE), National Astronomical Observatory of China, New Mexico State University, New York University, University of Notre Dame, Observat{\'o}rio Nacional/MCTI, The Ohio State University, Pennsylvania State University, Shanghai Astronomical Observatory, United Kingdom Participation Group, Universidad Nacional Autonoma de Mexico, University of Arizona, University of Colorado Boulder, University of Oxford, University of Portsmouth, University of Utah, University of Virginia, University of Washington, University of Wisconsin, Vanderbilt University and Yale University. Funding Information: The authors thank the anonymous referee for their careful reading of the paper and their constructive comments. This work benefited from the THALES project 383549 that is jointly funded by the European Union and the Greek Government in the framework of the programme {\textquoteleft}Education and lifelong learning{\textquoteright}. JA acknowledges support from ERC Advanced Grant FEEDBACK 340442. AS acknowledges support by JSPS KAKENHI Grant Number 26800098. Funding for the Sloan Digital Sky Survey IV has been provided by the Alfred P. Sloan Foundation, the U.S. Department of Energy Office of Science and the Participating Institutions. SDSS acknowledges support and resources from the Center for High-Performance Computing at the University of Utah. The SDSS web site is www.sdss.org. SDSS is managed by the Astrophysical Research Consortium for the Participating Institutions of the SDSS Collaboration including the Brazilian Participation Group, the Carnegie Institution for Science, Carnegie Mellon University, the Chilean Participation Group, the French Participation Group, Harvard-Smithsonian Center for Astrophysics, Instituto de As-trof{\'i}sica de Canarias, The Johns Hopkins University, Kavli Institute for the Physics and Mathematics of the Universe (IPMU)/University of Tokyo, Lawrence Berkeley National Laboratory, Leibniz Insti-tut f{\"u}r Astrophysik Potsdam (AIP), Max-Planck-Institut f{\"u}r As-tronomie (MPIA Heidelberg), Max-Planck-Institut f{\"u}r Astrophysik (MPA Garching), Max-Planck-Institut f{\"u}r Extraterrestrische Physik (MPE), National Astronomical Observatory of China, New Mexico State University, New York University, University of Notre Dame, Observat{\'o}rio Nacional/MCTI, The Ohio State University, Pennsylvania State University, Shanghai Astronomical Observatory, United Kingdom Participation Group, Universidad Nacional Autonoma de Mexico, University of Arizona, University of Colorado Boulder, University of Oxford, University of Portsmouth, University of Utah, University of Virginia, University of Washington, University of Wisconsin, Vanderbilt University and Yale University. Publisher Copyright: {\textcopyright} 2018 The Author(s).",
year = "2017",
month = oct,
doi = "10.1093/mnras/stx1602",
language = "English (US)",
volume = "471",
pages = "1976--2001",
journal = "Monthly Notices of the Royal Astronomical Society",
issn = "0035-8711",
publisher = "Oxford University Press",
number = "2",
}