Publication Date:
2016-03-03
Description:
We investigate the relation between star formation rates ( $\dot{{M}}_s$ ) and AGN properties in optically selected type 1 quasars at 2 〈 z 〈 3 using data from Herschel and the SDSS. We find that $\dot{{M}}_s$ remains approximately constant with redshift, at 300 ± 100 M yr –1 . Conversely, $\dot{{M}}_s$ 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 between $\dot{{M}}_s$ and black hole accretion rate ( $\dot{{M}}_{{\rm bh}}$ ) existing in only parts of the $z-\dot{{M}}_{s}-\dot{{M}}_{{\rm bh}}$ plane, dependent on the free gas fraction, the trigger for activity, and the processes that may quench star formation. The relations between $\dot{{M}}_s$ 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 between $\dot{{M}}_s$ and $\dot{{M}}_{{\rm bh}}$ . Finally, there is no strong relation between $\dot{{M}}_s$ 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.
Print ISSN:
0035-8711
Electronic ISSN:
1365-2966
Topics:
Physics
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