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Accepted for publication in ApJ on January 19th 2001. Analysis of PG quasar observations suggests a nonlinear relation between the black hole mass, MBH, and the bulge mass, Mbulge, although a linear relation, as proposed for nearby galaxies, cannot be ruled out. New MBH values for nearby galaxies from Gebhardt et al., and Lbulge measurements for Seyfert 1 galaxies from Virani et al., are used here to obtain a more accurate value for the slope of the MBH–Mbulge relation. The combined sample of 40 active and non-active galaxies suggests a significantly nonlinear relation, MBH ∝ M 1.53±0.14 bulge. Further support for a nonlinear relation is provided by the slope of the MBH–stellar velocity dispersion relation found recently, and by the low MBH found in late type spiral galaxies. The mean MBH/Mbulge ratio is therefore not a universal constant, but rather drops from ∼ 0.5 % in bright (MV ∼ −22) ellipticals, to ∼ 0.05% in low luminosity (MV ∼ −18) bulges. Hubble Space Telescope determinations of MBH in late type spirals, and of the bulge magnitude in narrow line Seyfert 1 galaxies (both predicted to have low MBH), can further test the validity of the nonlinear MBH–Mbulge relation. Subject headings: galaxies: nuclei-quasars: general 1
Ari Laor (Fri,) studied this question.