Downsizing of supermassive black holes from the SDSS quasar survey - II. Extension to z ∼ 4

Abstract

Starting from the quasar sample of the Sloan Digital Sky Survey (SDSS) for which the C iv line is observed, we use an analysis scheme to derive the z-dependence of the maximum mass of active black holes, which overcomes the problems related to the Malmquist bias. The same procedure is applied to the low-redshift sample of SDSS quasars for which Hβ measurements are available. Combining with the results from the previously studied Mg ii sample, we find that the maximum mass of the quasar population increases as (1 + z) 1.64±0.04 in the redshift range 0.1 ≳ z ≳ 4, which includes the epoch of maximum quasar activity. © 2009 RAS.