The evolution of star formation in quasar host galaxies
  We have used far-infrared data from IRAS, ISO, SWIRE, SCUBA and MAMBO to
constrain statistically the mean far-infrared luminosities of quasars. Our
quasar compilation at redshifts 0<z<6.5 and I-band luminosities -20<I(AB)<-32
is the first to distinguish evolution from quasar luminosity dependence in such
a study. We carefully cross-calibrate IRAS against Spitzer and ISO, finding
evidence that IRAS 100um fluxes at <1Jy are overestimated by ~30%. We find
evidence for a correlation between star formation in quasar hosts and the
quasar optical luminosities, varying as SFR proportional to L_opt^(0.44+/-0.07)
at any fixed redshift below z=2. We also find evidence for evolution of the
mean star formation rate in quasar host galaxies, scaling as (1+z)^(1.6+/-0.3)
at z<2 for any fixed quasar I-band absolute magnitude fainter than -28. We find
no evidence for any correlation between star formation rate and black hole mass
at 0.5<z<4. Our data are consistent with feedback from black hole accretion
regulating stellar mass assembly at all redshifts.
