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

摘要

Several independent lines of evidence now point to a correlation betweenblack hole mass, M_bh, and radio-luminosity. In this paper we discuss thecorrelation for quasars from the FIRST Bright Quasar Survey (FBQS), using blackhole mass estimates from Hbeta linewidths. The FBQS objects fill in the gapbetween the radio-loud and radio-quiet quasars in the radio-luminosity -optical-luminosity plane, and we find that they fill the corresponding gap inthe M_bh - radio luminosity correlation. There is thus a continuous variationof radio luminosity with M_bh, and no evidence for a ``switch'' at some set ofcritical parameter values which turns on powerful radio jets. By combining theFBQS data with that for quasars from the Palomar-Green survey we find evidencefor a dependence of radio-luminosity on accretion rate relative to theEddington limit, L/L_Edd, as well as on M_bh, consistent with the well-knownradio-optical correlation for radio-loud quasars. We therefore suggest a newscheme to ``unify'' radio-loud and radio-quiet objects in which radioluminosity scales proportional to M_bh^{1.9+/-0.2}(L/L_Edd)^{1.0} forL/L_Edd~0.1, with an apparently weaker accretion rate dependence at lowL/L_Edd. The scatter about this relation is +/-1.1 dex, and may well hidesignificant contributions from other physical effects, such as black hole spinand radio source environment.