2001ApJ...553..677L

Analysis of (Palomar-Green) PG quasar observations suggests a nonlinear relation between the black hole mass, M_BH, and the bulge mass, M_bulge, although a linear relation, as proposed for nearby galaxies, cannot be ruled out. New M_BH values for nearby galaxies from K. Gebhardt et al., and L_bulge measurements for Seyfert 1 galaxies from S. N. Virani et al., are used here to obtain a more accurate value for the slope of the M_BH-M_bulge relation. The combined sample of 40 active and nonactive galaxies suggests a significantly nonlinear relation, M_BH∝M^1.53±0.14_bulge. Further support for a nonlinear relation is provided by the slope of the M_BH-stellar velocity dispersion relation found recently, and by the low M_BH found in late-type spiral galaxies. The mean M_BH/M_bulge ratio is therefore not a universal constant, but rather drops from ∼0.5% in bright (M_V~-22) ellipticals to ∼0.05% in low-luminosity (M_V~-18) bulges. Hubble Space Telescope determinations of M_BH in late-type spirals, and of the bulge magnitude in narrow-line Seyfert 1 galaxies (both predicted to have low M_BH), can further test the validity of the nonlinear M_BH-M_bulge relation.