On the Black Hole Mass-Bulge Mass Relation

We have reexamined the relation between the mass of the central black holes in nearby galaxies, M_bh, and the stellar mass of the surrounding spheroid or bulge, M_bulge. For a total of 30 galaxies bulge masses were derived through Jeans equation modeling or adopted from dynamical models in the literature. In stellar mass-to-light ratios, the spheroids and bulges span a range of a factor of 8. The bulge masses were related to well-determined black hole masses taken from the literature. With these improved values for M_bh, compared to Magorrian et al., and our redetermination of M_bulge, we find that the M_bh-M_bulge relation becomes very tight. We find M_bh ~ M with an observed scatter of ≲0.30 dex, a fraction of which can be attributed to measurement errors. The scatter in this relation is therefore comparable to the scatter in the relations of M_bh with σ and the stellar concentration. These results confirm and refine the work of Marconi & Hunt. For M_bulge ~ 5 × 10¹⁰ M_☉ the median black hole mass is 0.14% ± 0.04% of the bulge mass.