A study of quasar radio emission from the VLA first survey

Abstract

Using the most recent (1998) version of the VLA FIRST survey radio catalog, we have searched for radio emission from 1704 quasars taken from the most recent (1993) version of the Hewitt & Burbidge quasar catalog. These quasars lie in the roughly 5000 deg² of sky already covered by the VLA FIRST survey. Our work has resulted in positive detection of radio emission from 389 quasars, of which 69 quasars have been detected for the first time at radio wavelengths. We find no evidence of a correlation between optical and radio luminosities for optically selected quasars. We find indications of a bimodal distribution of radio luminosity, even at a low flux limit of 1 mJy. We show that radio luminosity is a good discriminant between radio-loud and radio-quiet quasar populations, and that it may be inappropriate to make such a division on the basis of the radio-to-optical luminosity ratio. We discuss the dependence of the radio-loud fraction on optical luminosity and redshift.