Molecular Gas in Dual and Single AGN in Mergers

Mergers of gas-rich galaxies result in rapid formation of new stars and growth of supermassive black holes (SMBHs). The prevailing paradigm for galaxy formation includes feedback from growing SMBHS (i.e., active galactic nuclei or AGN) as a key ingredient in explaining the colors and stellar masses of the galaxies we see in the Universe around us. Galaxy mergers are also the likely source of eventual mergers of SMBHs; we have evidence that SMBHs do merge, but we lack a good understanding of how often they merge and how massive they are when they merge. Studying galaxy mergers and the properties of the pre-merger SMBHs can constrain both the merger frequency and the masses (e.g., do they grow significantly from gas accretion before they merge or does the final merged SMBH grow significantly).

In “Molecular Gas in Major Mergers Hosting Dual and Single AGN at <10 kpc Nuclear Separations” (Johnstone+) we study the molecular gas in the vicinity of the nuclei in galaxy mergers with two nuclei where at least one nucleus is an AGN. We find that whether a nucleus hosts an AGN does not seem directly dependent on the amount of gas in the vicinity. This suggests that whether we see zero, one, or two AGN in a galaxy merger is more dependent on small-scale processes (such as gas directly blocking our view of the AGN or variations in the amount of gas accreting onto the SMBH).

The paper has been accepted for publication in the Astrophysical Journal and a preprint is available at the link above.