The AGN-starburst connection, galactic superwinds, and MBH-σ

Recent observations of young galaxies at redshifts z similar to 3 have revealed simultaneous AGN and starburst activity, as well as galaxy-wide superwinds. I show that there is probably a close connection between these phenomena by extending an earlier treatment of the M-BH-sigma relation. As the black hole grows, an outflow drives a shell into the surrounding gas. This stalls after a dynamical time at a size determined by the hole's current mass and thereafter grows on the Salpeter timescale. The gas trapped inside this bubble cools, forms stars, and is recycled as accretion and outflow. The consequent high metallicity agrees with that commonly observed in AGN accretion. Once the hole reaches a critical mass, this region attains a size such that the gas can no longer cool efficiently. The resulting energy-driven flow expels the remaining gas as a superwind, fixing both the M-BH-sigma relation and the total stellar bulge mass at values in good agreement with observations. Black hole growth thus produces starbursts and ultimately a superwind.