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Enhanced star formation rates in AGN hosts with respect to inactive galaxies from PEP-Herschel observations | | P. Santini
; D. Rosario
; L. Shao
; D. Lutz
; R. Maiolino
; D. M. Alexander
; B. Altieri
; P. Andreani
; H. Aussel
; F. E. Bauer
; S. Berta
; A. Bongiovanni
; W. N. Brandt
; M. Brusa
; J. Cepa
; A. Cimatti
; E. Daddi
; D. Elbaz
; A. Fontana
; N. M. Forster Schreiber
; R. Genzel
; A. Grazian
; E. Le Floc'h
; B. Magnelli
; V. Mainieri
; R. Nordon
; A. M. Perez Garcia
; A. Poglitsch
; P. Popesso
; F. Pozzi
; L. Riguccini
; G. Rodighiero
; M. Salvato
; M. Sanchez-Portal
; E. Sturm
; L. J. Tacconi
; I. Valtchanov
; S. Wuyts
; | | Date: |
20 Jan 2012 | | Abstract: | We compare the average star formation (SF) activity in X-ray selected AGN
hosts with mass-matched control inactive galaxies,including star forming and
quiescent sources, at 0.5<z<2.5. Recent observations carried out by PACS, the
60-210um Herschel photometric camera, in GOODS-S, GOODS-N and COSMOS allow us
to unbiasedly estimate the far-IR luminosity, and hence the SF properties, of
the two samples. Accurate AGN host stellar masses are measured by decomposing
their total emission into the stellar and nuclear components. We find a higher
average SF activity in AGN hosts with respect to non-AGNs. The level of SF
enhancement is modest (~0.26dex at ~3sigma) at low X-ray luminosities
(Lx<~10^43.5erg/s) and more pronounced (0.56dex at >10sigma) for bright AGNs.
However, when comparing to star forming galaxies only, AGN hosts are broadly
consistent with the locus of their ’main sequence’. We investigate the relative
far-IR luminosity distributions of active and inactive galaxies, and find a
higher fraction of PACS detected, hence normal and highly star forming systems
among AGN hosts. Although different interpretations are possible, we explain
our findings as a consequence of a twofold AGN growth path: faint AGNs evolve
through secular processes, with instantaneous AGN accretion not tightly linked
to the current total SF in the host, while luminous AGNs co-evolve with their
hosts through periods of enhanced AGN activity and SF, possibly through major
mergers. While an increased SF with respect to non-AGNs of similar mass is
expected in the latter, we interpret the modest SF offsets measured in low-Lx
AGN hosts as either a) generated by non-synchronous accretion and SF histories
in a merger scenario or b) due to possible connections between instantaneous SF
and accretion that can be induced by smaller scale (non-major merger)
mechanisms. Far-IR luminosity distributions favour the latter scenario. | | Source: | arXiv, 1201.4394 | | Services: | Forum | Review | PDF | Favorites | |
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