Calibrating the galaxy halo - Black hole relation based on the clustering of quasars

The relationship between the mass of a black-hole and the circular velocity of its host dark-matter halo is fundamental to the clustering length of quasars. The slow evolution of the clustering length with redshift inferred in the 2dF quasar redshift survey strongly favors a scenario where the central black-holes comprise a larger fraction of the host galaxy mass at higher redshifts. In a scenario where quasars are triggered by halo mergers, this scaling, in combination with observed number counts imply that quasars have an episodic lifetime that is set by the dynamical time of a galactic disk rather than by the Salpeter time.