The counts and the distribution of spectral indices of extragalactic radio sources

A simple model is presented which fully explains the frequency characteristics of the dependence of radio source counts and the dependence of spectral index distribution on flux frequency and interval. The hypothesis of Pauliny-Toth and Kellerman (1972) arguing the absence of a new radio source population that is making a significant contribution to the total number of objects observed at high frequencies is confirmed. Sources with plane or power spectra are found to have similar histories, in agreement with the evolutionary model of Condon (1989).