An Evolutionary Model for Quasars

Abstract

A simple, though not necessarily unique, model for the cosmic population dynamics of quasars is presented. This model incorporates a double evolutionary trend: (i) a strong luminosity evolution, the presence of which we have discussed previously (Zotov and Davidson 1970, 1973) and (ii) an evolution of total coordinate density. This double trend is the same as that already found to be applicable to the total radio source population, if account is taken only of radio characteristics (Davidson et at. 1971). The predictions of the scheme are compared with five sets of data, covering a wide range of frequencies and flux density limits, and they are found to give good agreement in all cases.