The Limited Role of Mergers in the Black Hole to Bulge Mass Relation
by Lahav, Carmit Gordon and Meiron, Yohai and Soker, Noam
10 pages, 3 figures, 2 tables
We examine the scatter in the correlation between black hole masses and their host bulge masses, and find that the increase of the scatter with mass suggests that mergers alone cannot produce the observed correlation. A simple merger scenario of small galaxies leads to a proportionality relation between the late-time black hole and bulge masses, with intrinsic scatter increasing along the ridge line of the relation as the square root of the mass. By examining a sample of 87 galaxies, we find that the scatter increases with mass more rapidly than expected from the merger-only explanation. We do not dispute that mergers play a role, but our results favour a universal feedback mechanism that works on all scales. We discuss the possibility that the feedback mechanism that operated during galaxy formation involved the presence of a cooling flow.