The co-evolution of supermassive black holes and galaxies in luminous AGN over a wide range of redshift

It is well known that supermassive black holes (SMBHs) and their host galaxies co-evolve. A manifestation of this co-evolution is the correlation that has been found between the SMBH mass, M-BH, and the galaxy bulge or stellar mass, M-*. The cosmic evolution of this relation, though, is still a matter of debate. In this work, we examine the M-BH - M-* relation, using 687 X-ray luminous (median log[L-X,L-2-10 (keV)(ergs(-1))] = 44.3), broad-line active galactic nuclei (AGN), at 0.2 < z < 4.0 (median z approximate to 1.4) that lie in the XMM-XXL field. Their M-BH and M-* range from 7.5 < log [M-BH (M-circle dot)] < & 9.5 and 10 < log [M-*(M-circle dot)] < 12, respectively. Most of the AGN live in star-forming galaxies and their Eddington ratios range from 0.01 to 1, with a median value of 0.06. Our results show that M-BH and M-* are correlated (r = 0.47 +/- 0.21, averaged over different redshift intervals). Our analysis also shows that the mean ratio of the M-BH and M-* does not evolve with redshift, at least up to z = 2 and has a value of log(M-BH/M-*)= - 2.44. The majority of the AGN (75%) are in a SMBH mass growth-dominant phase. In these systems, the M-BH - M-* correlation is weaker and their M-* tends to be lower (for the same M-BH) compared to systems that are in a galaxy mass growth phase. Our findings suggest that the growth of black hole mass occurs first, while the early stellar mass assembly may not be so efficient.