The Radio Luminosity–Black Hole Mass Correlation for Quasars from the FIRST Bright Quasar Survey and a “Unification Scheme” for Radio-loud and Radio-quiet Quasars

Abstract

Several independent lines of evidence now point to a correlation between black hole mass Mbh and radio luminosity. In this Letter, we discuss the correlation for quasars from the FIRST Bright Quasar Survey (FBQS) using black hole mass estimates from Hβ line widths. The FBQS objects fill in the gap between the radio-loud and radio-quiet quasars in the radio luminosity-optical luminosity plane, and we find that they fill the corresponding gap in the Mbh-radio luminosity correlation. There is thus a continuous variation of radio luminosity with Mbh, and no evidence for a switch at some set of critical parameter values that turns on powerful radio jets. By combining the FBQS data with that for quasars from the Palomar-Green survey, we find evidence for a dependence of radio luminosity on accretion rate relative to the Eddington limit, L/LEdd, as well as on Mbh, consistent with the well-known radio-optical correlation for radio-loud quasars. We therefore suggest a new scheme to unify radio-loud and radio-quiet objects in which the radio luminosity scales proportional to M(L/LEdd)1.0 for L/LEdd ~ 0.1, with an apparently weaker accretion rate dependence at low L/LEdd. The scatter about this relation is ±1.1 dex and may well hide significant contributions from other physical effects, such as the black hole spin and radio source environment.