Black hole mass, velocity dispersion, and the radio source in active galactic nuclei

The recent discovery by Gebhardt et al. and Ferrarese & Merritt of a correlation between nuclear black hole mass M(bh) and stellar velocity dispersion a, in elliptical galaxies and spiral bulges has raised the question whether such a relationship exists for active galactic nuclei (AGNs). Estimates of M(bh) for many AGNs, made using reverberation mapping techniques, allow exploration of the relationship between black hole mass, the host galaxy, and the energetics of nuclear emission. However, since only a few AGNs have both M(bh) and a, measurements, we use the [O III] lambda 5007 emission-line widths on the assumption that for most AGNs the forbidden line kinematics are dominated by virial motion in the host galaxy bulge. We find that a relation does exist between M(bh) and the [O III] line width for AGNs, which is similar to the one found by Gebhardt et al., although with more scatter, as expected if secondary influences on the gas kinematics are also present. Our conclusion is that both active and inactive galaxies follow the same relationship between black hole mass and bulge gravitational potential. We find no compelling evidence for systematic differences in the mass estimates from reverberation mapping and stellar dynamics. We also find that for radio-quiet AGNs, the radio power and black hole mass are highly correlated, linking emission on scales of kiloparsecs with the nuclear energy source.