Star formation of X-ray AGN in COSMOS: The role of AGN activity and
  galaxy stellar mass
  We use $\sim 1,000$ X-ray sources in the COSMOS-Legacy survey and study the
position of the AGN relative to the star forming main sequence (MS). We also
construct a galaxy (non-AGN) reference sample that includes $\sim 90,000$
sources. We apply the same photometric selection criteria on both datasets and
construct their spectral energy distributions (SEDs) using optical to
far-infrared photometry compiled by the HELP project. We perform SED fitting,
using the X-CIGALE algorithm and the same parametric grid for both datasets, to
measure the star formation rate (SFR) and stellar mass of the sources. The mass
completeness of the data is calculated at different redshift intervals and is
applied on both samples. We define our own main sequence, based on the
distributions of the specific SFR at different redshift ranges and exclude
quiescent galaxies from our analysis. These allow us to compare the SFR of the
two populations in a uniform manner, minimizing systematics and selection
effects. Our results show that at low to moderate X-ray luminosities, AGN tend
to have lower or, at most, equal star formation rates compared to non-AGN
systems with similar stellar mass and redshift. At higher ($\rm L_{X,2-10keV} >
2-3\times 10^{44}\,erg\,s^{-1}$), we observe an increase of the SFR of AGN, for
systems that have $\rm 10.5 < log\,[M_*(M_\odot)] < 11.5$.
