On the Relationship between Radio Emission and Black Hole Mass in Galactic Nuclei

We use a comprehensive database of black hole masses (MBH) and nuclear luminosities to investigate the relationship between radio emission and MBH. Our sample covers a wide range of nuclear activity, from nearby inactive nuclei to classical Seyfert 1 nuclei and luminous quasars. Contrary to some previous studies, we find that the radio continuum power, either integrated for the entire galaxy or isolated for the core, correlates poorly with MBH. The degree of nuclear radio loudness, parameterized by the radio-to-optical luminosity ratio R, also shows no clear dependence on MBH. Radio-loud nuclei exist in galaxies with a wide range of MBH, from ∼ 106 M⊙ to a few×109 M⊙, and in a variety of hosts, from disk-dominated spirals to giant ellipticals. We demonstrate that R is strongly inversely correlated with L/LE, the ratio of nuclear luminosity to the Eddington luminosity, and hence with mass accretion rate. Most or all of the weakly active nuclei in nearby galaxies are radio-loud, highly sub-Eddington systems that are plausibly experiencing advection-dominated accretion. Subject headings: black hole physics — galaxies: active — galaxies: nuclei — galaxies: quasars — galaxies: Seyfert — radio continuum: galaxies