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

摘要

We present an analysis of the growth of black holes through accretion and bulges through star formation in 33 galaxies at the centers of cooling flows. Most of these systems show evidence of cavities in the intracluster medium (ICM) inflated by radio jets emanating from their active galactic nuclei (AGNs). We present a new and extensive analysis of X-ray cavities in these systems. We find that AGNs are energetically able to balance radiative losses (cooling) from the ICM in more than half of our sample. We examine the relationship between cooling and star formation and find that the star formation rates are approaching or are comparable to X-ray and far-UV limits on the rates of gas condensation onto the central galaxy. The vast gulf between radiative losses and the sink of cooling material, which has been the primary objection to cooling flows, has narrowed significantly. Using the cavity (jet) powers, we place strong lower limits on the rate of growth of the central black holes, and we find that they are growing at an average rate of ~0.1 M☉ yr-1, with some systems growing as quickly as ~1 M☉ yr-1. We find a trend between bulge growth (star formation) and black hole growth that is approximately in accordance with the slope of the local (Magorrian) relation between black hole and bulge mass, but the scatter suggests that bulges and black holes do not necessarily grow in lockstep. Bondi accretion can power the low-luminosity sources, provided the nuclear gas density rises as ~r-1 to the Bondi radius, but is probably too feeble to fuel the most powerful outbursts.