Cosmic evolution of quasar clustering: implications for the host haloes

We present detailed clustering measurements from the 2dF QSO Redshift Survey (2QZ) in the redshift range 0. 810^12 Mₛun and that the mean mass of their host haloes has to be a few x 10^13 Mₛun. The observed clustering is consistent with assuming that the locally observed correlation between black-hole mass and host-galaxy circular velocity is still valid at z>1. From the fraction of haloes which contain active quasars, we infer that the characteristic quasar lifetime is tQ ~ a few x 10⁷ yr at z~1 and approaches 10⁸ yr at higher redshifts.