%0 Journal Article
%T The Mean Star Formation Rate of X-ray selected Active Galaxies and its Evolution from z=2.5: Results from PEP-Herschel
%A D. J. Rosario
%A P. Santini
%A D. Lutz
%A L. Shao
%A R. Maiolino
%A D. M. Alexander
%A B. Altieri
%A P. Andreani
%A H. Aussel
%A F. E. Bauer
%A S. Berta
%A A. Bongiovanni
%A W. N. Brandt
%A M. Brusa
%A J. Cepa
%A A. Cimatti
%A T. J. Cox
%A E. Daddi
%A D. Elbaz
%A A. Fontana
%A N. M. F£¿rster Schreiber
%A R. Genzel
%A A. Grazian
%A E. Le Floch
%A B. Magnelli
%A V. Mainieri
%A H. Netzer
%A R. Nordon
%A I. P¨¦rez Garcia
%A A. Poglitsch
%A P. Popesso
%A F. Pozzi
%A L. Riguccini
%A G. Rodighiero
%A M. Salvato
%A M. Sanchez-Portal
%A E. Sturm
%A L. J. Tacconi
%A I. Valtchanov
%A S. Wuyts
%J Physics
%D 2012
%I arXiv
%R 10.1051/0004-6361/201219258
%X (Abridged) We study relationships between the SFR and the nuclear properties of X-ray selected AGNs out to z=2.5, using far-IR data in three extragalactic deep fields as part of the PACS Evolutionary Probe (PEP) program. Guided by studies of intrinsic infra-red AGN SEDs, we show that the majority of the FIR emission in AGNs is produced by cold dust heated by star-formation. We uncover characteristic redshift-dependent trends between the mean FIR luminosity (L_fir) and accretion luminosity (L_agn) of AGNs. At low AGN luminosities, accretion and SFR are uncorrelated at all redshifts, consistent with a scenario where most low-luminosity AGNs are primarily fueled by secular processes in their host galaxies. At high AGN luminosities, a significant correlation is observed between L_fir and L_agn, but only among AGNs at low and moderate redshifts (z<1). We interpret this as a signature of the increasing importance of major-mergers in driving both the growth of super-massive black holes (SMBHs) and global star-formation in their hosts at high AGN luminosities. However, we also find that the enhancement of SFR in luminous AGNs weakens or disappears at high redshifts (z>1). This suggests that the role of mergers in SMBH-galaxy co-evolution is less important at these epochs. At all redshifts, we find essentially no relationship between L_fir and nuclear obscuration across five orders of magnitude in obscuring column density, suggesting that various different mechanisms are likely to be responsible for obscuring X-rays in active galaxies. We explain our results within a scenario in which two different modes of SMBH fueling operate among low- and high-luminosity AGNs. We postulate, guided by emerging knowledge about the properties of high redshift galaxies, that the dominant mode of accretion among high-luminosity AGNs evolves with redshift.
%U http://arxiv.org/abs/1203.6069v2