Star formation rates in luminous quasars at 2 <z< 3

Abstract

We investigate the relation between star formation rates (Ṁ s ) and AGN properties in optically selected type 1 quasars at 2 < z < 3 using data from Herschel and the SDSS. We find thatṀ s remains approximately constant with redshift, at 300 ± 100 M ⊙ yr −1 . Conversely,Ṁ s increases with AGN luminosity, up to a maximum of ∼ 600 M ⊙ yr −1 , and with C iv FWHM. In context with previous results, this is consistent with a relation betweenṀ s and black hole accretion rate (Ṁ bh ) existing in only parts of the z −Ṁ s −Ṁ bh plane, dependent on the free gas fraction, the trigger for activity, and the processes that may quench star formation. The relations betweenṀ s and both AGN luminosity and C iv FWHM are consistent with star formation rates in quasars scaling with black hole mass, though we cannot rule out a separate relation with black hole accretion rate. Star formation rates are observed to decline with increasing C iv equivalent width. This decline can be partially explained via the Baldwin effect, but may have an additional contribution from one or more of three factors; M i is not a linear tracer of L 2500 , the Baldwin effect changes form at high AGN luminosities, and high C iv EW values signpost a change in the relation betweenṀ s andṀ bh . Finally, there is no strong relation betweenṀ s and Eddington ratio, or the asymmetry of the C iv line. The former suggests that star formation rates do not scale with how efficiently the black hole is accreting, while the latter is consistent with C iv asymmetries arising from orientation effects.

UV-luminous, star-forming hosts of z ∼ 2 reddened quasars in the Dark Energy Survey

“…7) is consistent with the work of Harris et al (2016), who find the SFRs of type-1 quasar host galaxies at 2 < z < 3 to increase with AGN luminosity up to some limiting rate. Shao et al (2010) and Netzer (2009) find a similar trend among high luminosity AGN (L bol > 10 44 ergs −1 ), but find no such dependency in lower luminosity systems -a result confirmed by independent studies of moderate-luminosity AGN (e.g.…”

“…To analyse the hosts of more luminous quasars, studies have primarily relied on observations at longer wavelengths in the far infra-red (FIR) to millimetre regime, where the host galaxy emission peaks (e.g. Priddey et al 2003;Harris et al 2016). Unlike their low-redshift and lower-luminosity counterparts, the SFRs of high-luminosity quasars at z 2 have been shown to correlate with L bol,QSO , with several studies finding more luminous quasars to reside in more actively star-forming hosts (e.g.…”

“…Unlike their low-redshift and lower-luminosity counterparts, the SFRs of high-luminosity quasars at z 2 have been shown to correlate with L bol,QSO , with several studies finding more luminous quasars to reside in more actively star-forming hosts (e.g. Coppin et al 2008;Hatziminaoglou et al 2010;Rosario et al 2013;Delvecchio et al 2015;Xu et al 2015;Harris et al 2016).…”

The Circumgalactic Medium of Submillimeter Galaxies. II. Unobscured QSOs within Dusty Starbursts and QSO Sightlines with Impact Parameters below 100 kpc

“…For comparison, we show the average AGN bolometric luminosities vs. the average IR luminosities for samples of star-forming galaxies. Note the different AGN tracers that were used to estimate the bolometric luminosity: for our SMG-QSO composites we used the luminosity at 1350Å, Rafferty et al Harris et al 2016), confirming that the IR emission is dominated by unusually high star formation activity (consistent with the observation in Figure 5). …”

The Geometry of the Infrared and X-Ray Obscurer in a Dusty Hyperluminous Quasar

“…Moreover, there is evidence for a deep connection between starburst and active galactic nucleus (AGN) activity at all redshifts, from, for example, the -s M bh relation (e.g., Magorrian et al 1998;Tremaine et al 2002), and from the presence of starbursts and AGNs in the same systems (Genzel et al 1998;Farrah et al 2003;Alexander et al 2005;Lonsdale et al 2006, p. 285, Hernán-Caballero et al 2009Harris et al 2016) at rates much higher than expected by chance. There is also evidence that star formation and AGN activity can directly affect each other (see Fabian 2012 for a review), via both quenching (e.g., Croton et al 2006;Chung et al 2011;Farrah et al 2012;Alatalo et al 2015;Schaye et al 2015) and triggering (e.g., King 2005;Gaibler et al 2012;Ishibashi & Fabian 2012;Silk 2013;Zubovas et al 2013).…”