The Feedback‐regulated Growth of Black Holes and Bulges through Gas Accretion and Starbursts in Cluster Central Dominant Galaxies

Abstract

We present an analysis of the growth of black holes through accretion and\nbulges through star formation in 33 galaxies at the centers of cooling flows.\nMost of these systems show evidence of cavities in the intracluster medium\n(ICM) inflated by radio jets emanating from their active galactic nuclei (AGN).\nWe present a new and extensive analysis of X-ray cavities in these systems. We\nfind that AGN are energetically able to balance radiative losses (cooling) from\nthe ICM in more than half of our sample. Using a subsample of 17 systems, we\nexamine the relationship between cooling and star formation. We find that the\nstar formation rates are approaching or are comparable to X-ray and far UV\nlimits on the rates of gas condensation onto the central galaxy. The remaining\nradiative losses could be offset by AGN feedback. The vast gulf between\nradiative losses and the sink of cooling material, which has been the primary\nobjection to cooling flows, has narrowed and, in some cases, is no longer a\nserious issue. Using the cavity (jet) powers, we place strong lower limits on\nthe rate of growth of supermassive black holes in central galaxies, and we find\nthat they are growing at an average rate of ~ 0.1 solar masses per year, with\nsome systems growing as quickly as ~ 1 solar mass per year. We find a trend\nbetween bulge growth (star formation) and black hole growth that is\napproximately in accordance with the slope of the local (Magorrian) relation\nbetween black hole and bulge mass. However, the large scatter in the trend\nsuggests that bulges and black holes do not always grow in lock step.\n(Abridged)\n