Optical identification/flux density relationship for radio galaxies

Abstract

Optical identification statistics are summarized over a flux-density range of about 1000:1 at 408 MHz for identifying galaxies made on the Palomar Sky Survey (PSS) prints from various surveys. The percentage identification of galaxies seen on PSS is found to decrease from about 60% for a flux density of about 15 Jy at 408 MHz to about 15% at 1 Jy and approximately 10% at 25 mJy. The observed relationship between percentage identification and flux density, PI(S), is compared with the predictions of theoretical models of radio luminosity function derived by Wall et al. (1977) and Robertson (1980) on the basis of radio source counts and luminosity distribution of strong radio sources. Rather than assuming a standard optical luminosity for all radio galaxies, consideration is given to the available information on their bivariate radio-optical luminosity function.