VLA observations of objects in the Palomar Bright Quasar Survey

Abstract

All 114 objects from the Palomar Bright Quasar Survey (BQS) have been observed using the VLA at 5 GHz (6 cm) wavelength with 18 arcsec resolution. The new radio observations typically reach a level of 0. 1 in the ratio R of radio-to-optical luminosity which allow radio emission to be detected from most of the BQS objects. Ninety six (84%) of the BQS were detected as radio sources above a 3 σ level of 0.2 mJy, and 75 (82%) of the complete sample of 92 quasars with M_B_ < -23 were detected. There appears to be no difference in the radio properties of AGNs (M_B_ > 23) and quasars (M_B_ < 23). The distribution of radio flux density for the BQS sample appears bimodal. Most of the BQS quasars are "radio quiet" and have a radio flux density close to that of the optical flux density, but 15% - 20% are "radio loud" and are much brighter at radio than at optical wavelengths. Only a few percent of the BQS sample overlap radio-selected quasars in the ratio of radio-to-optical flux density. Most of the sources detected with 18 arcsec resolution were reobserved with a resolution of 0.5 arcsec. For the optically selected quasars, we find an increasing fraction of compact sources with increasing redshift. We derive the radio luminosity function, assuming that it is either (a) independent of optical luminosity, or (b) a function of the ratio R of radio-to-optical luminosity. The statistics of radio detections of optically selected quasars in this and in other published studies are equally well represented by the two cases. The radio emission from high-redshift quasars (z > 0.5) is dominated by compact components; quasars with R > 100 mostly have small redshifts. The distinction between the radio-loud and radio-quiet quasars from this optically selected sample cannot be explained simply by the effects of geometry and relativistic beaming for objects having a fixed ratio of intrinsic radio and optical luminosity.