Black hole accretion and host galaxies of obscured quasars in XMM-COSMOS
Creators: name: Mainieri, V.
name: Bongiorno, A.
name: Merloni, A.
name: Aller, M.
name: Carollo, M.
name: Iwasawa, K.
name: Koekemoer, A. M.
name: Mignoli, M.
name: Silverman, J. D.
name: Bolzonella, M.
name: Brusa, M.
name: Comastri, A.
name: Gilli, R.
name: Halliday, C.
name: Ilbert, O.
name: Lusso, E.
name: Salvato, M.
name: Vignali, C.
name: Zamorani, G.
name: Contini, T.
name: Kneib, J. -P.
name: Fevre, O. Le
name: Lilly, S.
name: Renzini, A.
name: Scodeggio, M.
name: Balestra, I.
name: Bardelli, S.
name: Caputi, K.
name: Coppa, G.
name: Cucciati, O.
name: de la Torre, S.
name: de Ravel, L.
name: Franzetti, P.
name: Garilli, B.
name: Iovino, A.
name: Kampczyk, P.
name: Knobel, C.
name: Kovac, K.
name: Lamareille, F.
name: Borgne, J. -F. Le
name: Brun, V . Le
name: Maier, C.
name: Nair, P.
name: Pello, R.
name: Peng, Y.
name: Montero, E. Perez
name: Pozzetti, L.
name: Ricciardelli, E.
name: Tanaka, M.
name: Tasca, L.
name: Tresse, L.
name: Vergani, D.
name: Zucca, E.
name: Aussel, H.
name: Capak, P.
name: Cappelluti, N.
name: Elvis, M.
name: Fiore, F.
name: Hasinger, G.
name: Impey, C.
name: Floc'h, E. Le
name: Scoville, N.
name: Taniguchi, Y.
name: Trump, J.
Publisher: name: arXiv
Year: 2011
Subjects: subject: Cosmology and Nongalactic Astrophysics (astro-ph.CO)
subject: FOS: Physical sciences
subject: FOS: Physical sciences

description: We explore the connection between black hole growth at the center of obscured quasars selected from the XMM-COSMOS survey and the physical properties of their host galaxies. We study a bolometric regime ( 8 x 10^45 erg/s) where several theoretical models invoke major galaxy mergers as the main fueling channel for black hole accretion. We confirm that obscured quasars mainly reside in massive galaxies (Mstar&gt;10^10 Msun) and that the fraction of galaxies hosting such powerful quasars monotonically increases with the stellar mass. We stress the limitation of the use of rest-frame color-magnitude diagrams as a diagnostic tool for studying galaxy evolution and inferring the influence that AGN activity can have on such a process. We instead use the correlation between star-formation rate and stellar mass found for star-forming galaxies to discuss the physical properties of the hosts. We find that at z ~1, ~62% of Type-2 QSOs hosts are actively forming stars and that their rates are comparable to those measured for normal star-forming galaxies. The fraction of star-forming hosts increases with redshift: ~71% at z ~2, and 100% at z ~3. We also find that the the evolution from z ~1 to z ~3 of the specific star-formation rate of the Type-2 QSO hosts is in excellent agreement with that measured for star-forming galaxies. From the morphological analysis, we conclude that most of the objects are bulge-dominated galaxies, and that only a few of them exhibit signs of recent mergers or disks. Finally, bulge-dominated galaxies tend to host Type-2 QSOs with low Eddington ratios (lambda&lt;0.1), while disk-dominated or merging galaxies have at their centers BHs accreting at high Eddington ratios (lambda &gt; 0.1).
description: Accepted by A&amp;A. 20 pages, 16 figures, 2 tables. A version with higher resolution figures and SED fits of Appendix A is available at http://www.eso.org/~vmainier/QSO2/qso2.pdf