The cosmic growth of the active black hole population at 1
Date Issued
2015
Author(s)
Schulze, A.
•
•
Gavignaud, I.
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Schramm, M.
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Silverman, J.
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Merloni, A.
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Zamorani, G.
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Hirschmann, M.
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Mainieri, V.
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Wisotzki, L.
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Shankar, F.
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•
Koekemoer, A. M.
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Temporin, G.
Description
We thank Knud Jahnke for fruitful discussions on this work and Micol Bolzonella for providing the zCOSMOS target sampling rates. AS acknowledges support by the China Postdoctoral Scientific Foundation, grant 2012M510256. This work was supported by World Premier International Research Center Initiative (WPI Initiative), MEXT, Japan. ABs work is supported by the INAF-Fellowship Programme and through PRIN-INAF 2011 ‘BH growth and AGN feedback through the cosmic time’. IG acknowledges support from FONDECYT through grant 11110501. MH acknowledges financial support from the European Research Council under the European Community's Seventh Framework Programme (FP7/2007-2013)/ERC grant agreement no. 202781 and from the European Research Council via an Advanced Grant under grant agreement no. 321323 NEOGAL. This research is based on the observations made with ESO Telescopes at the La Silla or Paranal Observatories under programme ID 175.A-0839. We gratefully acknowledge the contribution of the entire VVDS and COSMOS collaborations. Funding for the SDSS and SDSS-II was provided by the Alfred P. Sloan Foundation, the Participating Institutions, the National Science Foundation, the US Department of Energy, the National Aeronautics and Space Administration, the Japanese Monbukagakusho, the Max Planck Society and the Higher Education Funding Council for England. The SDSS website is http://www.sdss.org/ .
Abstract
We present a census of the active black hole population at 1 < z < 2, by constructing the bivariate distribution function of black hole mass and Eddington ratio, employing a maximum likelihood fitting technique. The study of the active black hole mass function (BHMF) and the Eddington ratio distribution function (ERDF) allows us to clearly disentangle the active galactic nuclei (AGN) downsizing phenomenon, present in the AGN luminosity function, into its physical processes of black hole mass downsizing and accretion rate evolution. We are utilizing type-1 AGN samples from three optical surveys (VVDS, zCOSMOS and SDSS), that cover a wide range of 3 dex in luminosity over our redshift interval of interest. We investigate the cosmic evolution of the AGN population as a function of AGN luminosity, black hole mass and accretion rate. Compared to z = 0, we find a distinct change in the shape of the BHMF and the ERDF, consistent with downsizing in black hole mass. The active fraction or duty cycle of type-1 AGN at z ̃ 1.5 is almost flat as a function of black hole mass, while it shows a strong decrease with increasing mass at z = 0. We are witnessing a phase of intense black hole growth, which is largely driven by the onset of AGN activity in massive SMBHs (supermassive black holes) towards z = 2. We finally compare our results to numerical simulations and semi-empirical models and while we find reasonable agreement over certain parameter ranges, we highlight the need to refine these models in order to match our observations.
Volume
447
Issue
3
Start page
2085
Issn Identifier
0035-8711
Ads BibCode
2015MNRAS.447.2085S
Rights
open.access
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