Abundance and evolution of radio-loud quasars in cold dark matter cosmology

The power of the jets and radio activity of quasars appears to be determined by the spin parameter of the black holes in the host galaxies. In this paper, the space number density of radio-loud quasars in cold dark matter cosmologies with biasing factors bf = 1 and bf = 1.5 is computed, assuming that radio-loud quasars are created when two galaxies merge, forming a rapidly spinning black hole in the center. Our results are consistent with the observational data if quasars have lifetimes of ~107-108 yr. Our present model supports the idea that some of the luminous radio galaxies may not contain a quasar in their centers.