Disentangling the AGN and Star-Formation connection using XMM-Newton
  There is growing evidence supporting the coeval growth of galaxies and their
resident SMBH. Most studies also claim a correlation between the activity of
the SMBH and the star-formation of the host galaxy. It is unclear, though,
whether this correlation extends to all redz and LX. In this work, we use data
from the X-ATLAS and XMM-XXL North fields and compile the largest X-ray sample
up to date, to investigate how X-ray AGN affect the star-formation of their
host galaxies in a wide redz and luminosity baseline, i.e., 0.03<z<3 and log LX
(2-10 keV)= (41-45.5) ergs-1. Our sample consists of 3336 AGN. 1872 X-ray
objects have spectroscopic redz. For the remaining sources we calculate
photometric redz using TPZ, a machine-learning algorithm. We estimate stellar
masses (M*) and Star Formation Rates (SFRs) by applying SED fitting through the
CIGALE code, using optical, near-IR and mid-IR photometry. 608 of our sources
also have far-IR photometry (Herschel). We use these sources to calibrate the
SFR calculations of the rest of our X-ray sample. Our results show a
correlation between the LX and the SFR, at all redz and LX spanned by our
sample. We also find a dependence of the specific SFR (sSFR) on redz, while
there are indications that LX enhances the sSFR even at low redz. We then
disentangle the effects of M* and redz on the SFR and study again its
dependence on the LX. Towards this end, we use the Schreiber et al. formula to
estimate the SFR of main sequence galaxies that have the same stellar mass and
redshift as our X-ray AGN. Our analysis reveals that the AGN enhances the
star-formation of its host galaxy, when the galaxy lies below the main sequence
and quenches the star-formation of the galaxy it lives in, when the host lies
above the main sequence. Therefore, the effect of AGN on the SFR of the host
galaxy, depends on the location of the galaxy relative to the main sequence.
