Matthew Thorne

There is still contention to the origins and drivers behind the observed correlations between supermassive black holes (SMBHs) and their host galaxies. These relations are fundamental to our understanding of galaxy evolution. Whilst there is evidence that SMBHs grow via secular processes, major mergers have often been cited as the main instigators of SMBH, galaxy growth and the drivers of observed SMBH-galaxy correlations. However, recent studies of SMBHs within disk-dominated galaxies with growth histories free of significant mergers have found contradictory results on whether these black holes are consistent with the SMBH-stellar mass relation. We combine three samples of active disk-dominated galaxies, which have different selection methods and biases, and interrogate them in the context of a model that assumes we are likely observing the system’s first instances of significant SMBH growth. The samples, which span a combined redshift range of 0.02 z 0.25, a stellar mass range of 8.9 log M*/M_Sun 11.4 and a black hole mass range of 5.0 log M_BH/M_Sun 8.9 give consistent results within this framework, despite their significantly different selection methods and sampling of different parts of the relevant parameter space. Our combined analysis resolves the apparent contradiction between these three studies under a straightforward framework of merger-free black hole growth. This suggests that merger-free SMBH growth onto the well-established MBH-M* relation can precede major merger events