HerschelATLAS: The cosmic star formation history of quasar host galaxies

Abstract

We present a derivation of the star formation rate per comoving volume of quasar host galaxies, derived from stacking analyses of far-infrared to mm-wave photometry of quasars with redshifts 0 < z < 6 and absolute I-band magnitudes −22 > I AB > −32 We use the science demonstration observations of the first ∼ 16 deg 2 from the Herschel Astrophysical Terahertz Large Area Survey (H-ATLAS) in which there are 240 quasars from the Sloan Digital Sky Survey (SDSS) and a further 171 from the 2dF-SDSS LRG and QSO (2SLAQ) survey. We supplement this data with a compilation of data from IRAS, ISO, Spitzer, SCUBA and MAMBO. H-ATLAS alone statistically detects the quasars in its survey area at > 5σ at 250, 350 and 500 μm. From the compilation as a whole we find striking evidence of downsizing in quasar host galaxy formation: low-luminosity quasars with absolute magnitudes in the range −22 > I AB > −24 have a comoving star formation rate (derived from 100 μm rest-frame luminosities) peaking between redshifts of 1 and 2, while high-luminosity quasars with I AB < −26 have a maximum contribution to the star formation density at z ∼ 3. The volume-averaged star formation rate of −22 > I AB > −24 quasars evolves as (1 + z) 2.3±0.7 at z < 2, but the evolution at higher luminosities is much faster reaching (1 + z) 10±1 at −26 > I AB > −28. We tentatively interpret this as a combination of a declining major merger rate with time and gas consumption reducing fuel for both black hole accretion and star formation.

The mean star-forming properties of QSO host galaxies

“…However, a close correspondence between QSOs and recent starburst events is predicted even in co-evolutionary models that do not explicitly rely on major galaxy mergers to fuel QSOs (e.g., Ciotti & Ostriker 2007). Star formation (SF) in QSO host galaxies has been extensively studied using high-resolution imaging in the optical (e.g., Bahcall et al 1997;Dunlop et al 2003;Jahnke et al 2004) and near-infared (e.g., Kukula et al 2001;Guyon et al 2006;Veilleux et al 2009); emission line tracers such as the [O II] line (Hes et al 1993;Ho 2005;Silverman et al 2009;Kalfountzou et al 2012); mid-infrared emission lines and PAH features (Netzer et al 2007;Lutz et al 2008;Shi et al 2009); and farinfrared (FIR) and sub-mm photometry (e.g., Priddey et al 2003;Omont et al 2003;Lutz et al 2010;Serjeant & Hatziminaoglou 2009;Serjeant et al 2010;Bonfield et al 2011). In general, QSO hosts are in massive, spheroidally-dominated galaxies, which frequently show signs of on-going star-formation (e.g., Jahnke et al 2004;Trump et al 2013), though signatures of early stage mergers or strong disturbances are not particularly frequent (Dunlop et al 2003;Guyon et al 2006;Bennert et al 2008;Veilleux et al 2009).…”

Mid-Infrared-Selected Quasars. I. Virial Black Hole Mass and Eddington Ratios

“…In the merger-driven model these quasars are in an early transitional phase and are in the process of expelling their dusty environment before becoming "normal" blue quasars (type 1). This IR-luminous phase also evolves with time, and was more common at high z (e.g., Caputi et al 2007;Serjeant et al 2010). Optical studies of quasar and host systems are challenged by the high contrast between the bright-point-source quasar and starlight.…”

Akari All-Sky Bright Source Catalogue: Far-Infrared Luminous Quasars and the Optical Far-Infrared Correlation

“…For sources at z > 1, however, observed values are higher than predicted in every case, suggesting the flux from these sources may be magnified by gravitational lenses. Magnification by a lens would give a higher relative FIR luminosity, since there would not be the drop off at higher luminosity predicted by the Serjeant et al (2010) relation. If so, it provides a new method for identifying lenses by selecting quasars with strong FIR luminosity; if not, it identifies a new population of extreme starbursting quasars.…”

“…Stacking analysis of the initial observations from Herschel (Serjeant et al, 2010) has given the following relationship between 100 µm luminosity and absolute magnitude in the I-band for quasars:…”

“…Earlier work has attempted to overcome this deficiency by using stacking analysis, often of sources observed at a variety of far-infrared (FIR) and submillimetre wavelengths (Serjeant & Hatziminaoglou, 2009;Serjeant et al, 2010;Bonfield et al, 2011). This has led to the discovery of a correlation between the optical luminosity (primarily due to the quasar) and the FIR luminosity (primarily due to star formation).…”