On the black hole-bulge mass relation in active and inactive galaxies

Abstract

New black hole mass estimates are presented for a sample of 72 active galactic nuclei (AGNs) covering three decades in optical luminosity. Using a subsample of Seyfert galaxies, which have black hole mass estimates from both reverberation mapping and stellar velocity dispersions, we investigate the geometry of the AGNs’ broad-line region. It is demonstrated that a model in which the orbits of the line-emitting material have a flattened geometry is favoured over randomly-orientated orbits. Using this model we investigate the Mbh-Lbulge relation for a combined 90-object sample consisting of the AGNs plus a sample of 18 nearby inactive elliptical galaxies with dynamical black hole mass measurements. It is found that, for all reasonable mass-to-light ratios, the Mbh-Lbulge relation is equivalent to a linear scaling between bulge and black hole mass. The best-fitting normalization of the Mbh-Mbulge relation is found to be Mbh=0.0012Mbulge, in agreement with recent black hole mass studies based on stellar velocity dispersions. Furthermore, the scatter around the Mbh-Lbulge relation for the full sample is found to be significantly smaller than has been previously reported (Δlog Mbh=0.39 dex). Finally, using the nearby inactive elliptical galaxy sample alone, it is shown that the scatter in the Mbh-Lbulge relation is only 0.33 dex, comparable with that of the Mbh-σ relation. These results indicate that reliable black hole mass estimates can be obtained for high redshift galaxies.