Inferring a difference in the star-forming properties of lower versus higher X-ray luminosity AGNs

Abstract: We explore the distribution of RMS=SFR/SFR_MS (where SFR_MS is the star formation rate of "Main Sequence" star-forming galaxies) for AGN hosts at z=1. We split our sample into two bins of X-ray luminosity divided at Lx=2x10^43erg s-1 to investigate whether the RMS distribution changes as a function of AGN power. Our main results suggest that, when the RMS distribution of AGN hosts is modelled as a log-normal distribution (i.e. the same shape as that of MS galaxies), galaxies hosting more powerful X-ray AGNs (i.e. Lx>2x10^43erg s-1) display a narrower RMS distribution that is shifted to higher values compared to their lower Lx counterparts. In addition, we find that more powerful X-ray AGNs have SFRs that are more consistent with that of MS galaxies compared to lower Lx AGNs. Despite this, the mean SFRs (as opposed to RMS) measured from these distributions are consistent with the previously observed flat relationship between SFR and Lx. Our results suggest that the typical star-forming properties of AGN hosts change with Lx , and that more powerful AGNs typically reside in more MS-like star-forming galaxies compared to lower Lx AGNs.