Allevato, V. and Finoguenov, A. and Cappelluti, N. and Miyaji, T. and Hasinger, G. and Salvato, M. and Brusa, M. and Gilli, R. and Zamorani, G. and Shankar, F. and James, J. B. and McCraken, H. J. and Bongiorno, A. and Merloni, A. and Peacock, J. A. and Silverman, J. and Comastri, A. (2011) The XMM-Newton Wide Field Survey in the COSMOS Field: Redshift Evolution of AGN Bias and Subdominant Role of Mergers in Triggering Moderate-luminosity AGNs at Redshifts up to 2.2. Astrophysical Journal, 736 (2). Art. No. 99. ISSN 0004-637X http://resolver.caltech.edu/CaltechAUTHORS:20110830-071015865
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We present a study of the redshift evolution of the projected correlation function of 593 X-ray selected active galactic nuclei (AGNs) with I_(AB) < 23 and spectroscopic redshifts z < 4, extracted from the 0.5–2 keV X-ray mosaic of the 2.13 deg^2 XMM- Cosmic Evolution Survey (COSMOS). We introduce a method to estimate the average bias of the AGN sample and the mass of AGN hosting halos, solving the sample variance using the halo model and taking into account the growth of the structure over time. We find evidence of a redshift evolution of the bias factor for the total population of XMM-COSMOS AGNs from b(z = 0.92) = 2.30 ± 0.11 to b(z = 1.94) = 4.37 ± 0.27 with an average mass of the hosting dark matter (DM) halos log M_0(h^ (−1) M_☉) ~ 13.12 ± 0.12 that remains constant at all z < 2. Splitting our sample into broad optical line AGNs (BL), AGNs without broad optical lines (NL), and X-ray unobscured and obscured AGNs, we observe an increase of the bias with redshift in the range z = 0.7–2.25 and z = 0.6–1.5 which corresponds to a constant halo mass of log M_0(h ^(−1) M_☉) ~ 13.28 ± 0.07 and log M_0(h^(−1) M_☉) ~ 13.00 ± 0.06 for BL/X-ray unobscured AGNs and NL/X-ray obscured AGNs, respectively. The theoretical models, which assume a quasar phase triggered by major mergers, cannot reproduce the high bias factors and DM halo masses found for X-ray selected BL AGNs with L_(BOL) ~ 2×10^(45) erg s^(−1). Our work extends up to z ~ 2.2 the z ≾ 1 statement that, for moderate-luminosity X-ray selected BL AGNs, the contribution from major mergers is outnumbered by other processes, possibly secular ones such as tidal disruptions or disk instabilities.
|Additional Information:||© 2011 The American Astronomical Society. Received 2011 February 14; accepted 2011 April 30; published 2011 July 13. We gratefully acknowledge the contributions of the entire COSMOS collaboration consisting of more than 100 scientists. More information on the COSMOS survey is available at http://www.astro.caltech.edu/∼COSMOS. We thank the anonymous referee for carefully reading the manuscript and providing us with constructive remarks. V.A., G.H., and M.S. were supported by the German Deutsche Forschungsgemeinschaft, DFG Leibniz Prize (FKZ HA 850/28-1).|
|Subject Keywords:||dark matter; galaxies: active; galaxies: evolution; large-scale structure of universe; quasars: general; surveys|
|Classification Code:||PACS: 98.80.+p; 95.85.Nv; 98.62.Py; 95.35.+d; 98.62.Qz; 98.54.Cm|
|Official Citation:||The XMM-Newton Wide Field Survey in the COSMOS Field: Redshift Evolution of AGN Bias and Subdominant Role of Mergers in Triggering Moderate-luminosity AGNs at Redshifts up to 2.2 V. Allevato, A. Finoguenov, N. Cappelluti, T. Miyaji, G. Hasinger, M. Salvato, M. Brusa, R. Gilli, G. Zamorani, F. Shankar, J. B. James, H. J. McCracken, A. Bongiorno, A. Merloni, J. A. Peacock, J. Silverman and A. Comastri doi: 10.1088/0004-637X/736/2/99|
|Usage Policy:||No commercial reproduction, distribution, display or performance rights in this work are provided.|
|Deposited By:||Ruth Sustaita|
|Deposited On:||30 Aug 2011 14:55|
|Last Modified:||26 Dec 2012 13:38|
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