Herschel-ATLAS: The link between accretion luminosity and star formation
  in quasar host galaxies
  We use the science demonstration field data of the Herschel-ATLAS to study
how star formation, traced by the far-infrared Herschel data, is related to
both the accretion luminosity and redshift of quasars selected from the Sloan
Digital Sky Survey and the 2SLAQ survey. By developing a maximum likelihood
estimator to investigate the presence of correlations between the far-infrared
and optical luminosities we find evidence that the star-formation in quasar
hosts is correlated with both redshift and quasar accretion luminosity.
Assuming a relationship of the form L_IR \propto L_QSO^{\theta} (1 +
z)^{\zeta}, we find {\theta} = 0.22 +/- 0.08 and {\zeta} = 1.6 +/- 0.4,
although there is substantial additional uncertainty in {\zeta} of order +/- 1,
due to uncertainties in the host galaxy dust temperature. We find evidence for
a large intrinsic dispersion in the redshift dependence, but no evidence for
intrinsic dispersion in the correlation between L_QSO and L_IR, suggesting that
the latter may be due to a direct physical connection between star formation
and black hole accretion. This is consistent with the idea that both the quasar
activity and star formation are dependent on the same reservoir of cold gas, so
that they are both affected by the influx of cold gas during mergers or heating
of gas via feedback processes.
