The evolution of star formation in quasar host galaxies

TL;DR

This study analyzes the evolution of star formation in quasar host galaxies across a wide redshift range using infrared data, revealing correlations with optical luminosity and redshift, and supporting feedback regulation models.

Contribution

It provides the first statistical analysis distinguishing evolution from luminosity dependence in quasar host star formation using multi-instrument infrared data.

Findings

Star formation rate correlates with optical luminosity as SFR ∝ L_opt^0.44.

Star formation rate evolves with redshift as (1+z)^1.6 for z<2.

No correlation found between star formation rate and black hole mass at 0.5<z<4.

Abstract

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.