THE (BLACK HOLE)-BULGE MASS SCALING RELATION AT LOW MASSES

Several recent papers have reported on the occurrence of active galactic nuclei (AGNs) containing undermassive black holes relative to a linear scaling relation between black hole mass (M-bh) and host spheroid stellar mass (M-sph,M-*). However, dramatic revisions to the M-bh-M-sph,M-* and M-bh-L-sph relations, based on samples containing predominantly inactive galaxies, have recently identified a new steeper relation at M-bh less than or similar to (2-10) x10(8) M-circle dot, roughly corresponding toM(sph,*) less than or similar to (0.3-1) x 10(11) M-circle dot. We show that this steeper, quadratic-like M-bh-M-sph,M-* relation defined by the Sersic galaxies, i.e., galaxies without partially depleted cores, roughly tracks the apparent offset of the AGN having 10(5) less than or similar to M-bh/M-circle dot less than or similar to 0.5 x 10(8). That is, these AGNs are not randomly offset with low black hole masses, but also follow a steeper (nonlinear) relation. As noted by Busch et al., confirmation or rejection of a possible AGN offset from the steeper M-bh-M-sph,M-* relation defined by the Sersic galaxies will benefit from improved stellar mass-to-light ratios for the spheroids hosting these AGNs. Several implications for formation theories are noted. Furthermore, reasons for possible under-and overmassive black holes, the potential existence of intermediate mass black holes (<10(5) M-circle dot), and the new steep (black hole)-(nuclear star cluster) relation, M-bh proportional to M-nc(2.7 +/- 0.7), are also discussed.