So far, BHs have been discovered in every galaxy that contains a bulge and that has been observed with enough resolution to find a BH consistent with the correlations in Figure 2. The canonical BH is about 0.13% of the mass of the bulge; the scatter is more than a factor of 10. Table 2 lists the strongest BH mass limits. We fail to find BHs in pure disk and related galaxies. These are discussed in the next section.
Galaxy | Type | MB,nucleus | M upper limit | D | Reference | |
(M) | (km/s) | (Mpc) | ||||
M 33 | Scd | -10.21 | 1.0 e3 | 24 | 0.8 | Gebhardt + 2001 |
NGC 205 | Sph | -10 | 9.0 e4 | 15 | 0.72 | Jones + 1996 |
NGC 4395 | Sm | 8.0 e4 | 30 | 2.6 | Filippenko + 2001 | |
IC 342 | Scd | -14 | 5.0 e5 | 33 | 1.8 | Böker + 1999 |
Note - These galaxies do not contain bulges; the absolute magnitude MB,nucleus and velocity dispersion refer to the nuclear star cluster. NGC 205 is a spheroidal galaxy; it does not fit into the traditional Hubble Sequence, but it is physically related to late-type galaxies (Kormendy 1985, 1987). |