THE EVOLUTION OF THE QUASAR LUMINOSITY FUNCTION

In an earlier paper we presented quasar luminosity functions in three redshift bins, derived from a variability selected sample. Here we pro vide a major extension to this survey, with a view to improving statis tics and completeness, and extending the redshift range. The luminosit y functions for redshifts of less than 2.2 show a featureless power la w of the form phi = 10(beta(M-M0)), with no sign of a 'break'. The qua sar luminosity function is also derived for the redshift range 2.2<z<3 .2, which again shows a featureless power law, but with a steeper slop e. When the data are combined with a new sample of bright quasars, the quasar luminosity functions in all four redshift ranges are consisten t with a single power law of index beta = 0.63. Plots of quasar space density as a function of redshift in three luminosity bins are also pr esented and show strong evolution at low redshift, but nearly constant space density beyond a redshift of 2.