Analysis of 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 , can not be ruled out .
New M _ { BH } values for nearby galaxies from Gebhardt et al. , and L _ { bulge } measurements for Seyfert 1 galaxies from 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 non-active galaxies suggests a significantly nonlinear relation , M _ { BH } \propto M _ { bulge } ^ { 1.53 \pm 0.14 } .
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 \sim 0.5 % in bright ( M _ { V } \sim - 22 ) ellipticals , to \sim 0.05 % in low luminosity ( M _ { V } \sim - 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 .