THE COSMOLOGICAL EVOLUTION OF QUASARS WITH STEEP SPECTRA

Possible origins for the drop of the scintillating radio source count at weak flux densities (S-102 < 1 Jy) are analyzed. The most probable reason for this drop is the absence of quasars at high redshift. The s teeper decrease in the source count for compact sources compared to th at for extended radio sources is the result of a high birth rate for q uasars compared to radio galaxies. It is concluded that the shapes of the scintillating radio source count curve at low and high Aux densiti es reflect the cosmological evolution of quasars.