Star formation in galaxies hosting Active Galactic Nuclei up to z~1

TL;DR

This paper reviews evidence from the zCOSMOS survey indicating a strong link between star formation and AGN activity in galaxies up to redshift ~1, suggesting co-evolution of black holes and host galaxies.

Contribution

It provides new insights into the relationship between star formation rates and AGN activity, demonstrating their similar evolution and challenging previous assumptions based on luminosity-limited samples.

Findings

AGN star formation rates range from 1 to 100 solar masses per year.

AGN activity correlates with bluer galaxy colors and stellar mass.

The ratio of mass accretion rate to SFR remains constant up to z~1.

Abstract

We review recent evidence for a clear association between accretion onto supermassive black holes and star formation up to z~1 in the zCOSMOS survey. Star formation rates (SFRs) are determined from the [OII] emission-line strength and a correction for the AGN contribution. We find that SFRs of X-ray selected AGN span a distribution of 1-100 solar masses per year and evolve in a manner that is indistinguishable from that of massive, star-forming galaxies. The close relationship between AGN activity and star formation is further supported by an increase in the AGN fraction with bluer rest-frame colors (U-V); we further illustrate how the location of AGNs in a color-magnitude diagram can be misleading in luminosity-limited samples due to the dependence of AGN activity on the stellar mass and the low mass-to-light ratios of blue cloud galaxies. To conclude, our results support a co-evolutionary scenario up to z~1 based on the constancy with redshift of the ratio between mass accretion rate and SFR.