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

New black-hole mass estimates are presented for a sample of 72 AGN covering three decades in optical luminosity. Using a sub-sample of Seyfert galaxies, which have blackhole mass estimates from both reverberation mapping and stellar velocity dispersions, we investigate the geometry of the AGN broad-line region (BLR). 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 92-object sample, consisting of the AGN plus a sample of 20 nearby inactive 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 (∆ log Mbh = 0.39 dex). Finally, using the nearby inactive galaxy sample alone, it is shown that, again contrary to previous reports, the scatter in the Mbh − Lbulge relation in normal galaxies is only 0.31 dex, identical to that of the Mbh− σ relation. These results indicate that reliable black-hole mass estimates can be obtained for high redshift galaxies.