Contributed Talk - Splinter SMBHs

Wednesday, 23 September 2020, 16:10   (virtual room K)

The role of major mergers in triggering AGNs with the highest Eddington ratios

Victor Marian, Knud Jahnke et al.

Research over the past decade has shown inconsistent results with respect to major galaxy mergers being the dominating or even an important mechanism for the triggering of optically or X-ray selected active galactic nuclei (AGN) and the growth of supermassive black holes (SMBH) in galaxies. We test whether such a causal connection exists at least in the most ‘plausible’ part of AGN parameter space: the highest specific accretion rate broad-line AGNs at the peak epoch of black hole activity around z = 2 and in the local universe at z=0.2. We compare our AGN samples with stellar mass- and redshift-matched inactive galaxies and derive the respective merger fractions in order to determine a potential excess in the AGN’s merger rate, which would indicate a predominantly merger-induced origin. While we find no significant signs of major mergers being dominant in triggering high Eddington ratio AGNs at z=2, such gravitational encounters appear to be an important mechanism for similar AGNs at low redshift. In addition we report the merger fractions of similar galaxy samples taken from the cosmological IllustrisTNG simulation. This allows us to verify our observational results, but also to highlight any potential discrepancies in SMBH growth between observations and simulations.