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 (Mbh) and host spheroid stellar mass (Msph,∗). However, dramatic revisions to the Mbh-Msph,∗ and Mbh-Lsph relations, based on samples containing predominantly inactive galaxies, have recently identified a new steeper relation atMbh (2-10)×108 M , roughly corresponding toMsph,∗ (0.3-1)×1011 M .We show that this steeper, quadratic-likeMbh-Msph,∗ relation defined by the S´ersic galaxies, i.e., galaxies without partially depleted cores, roughly tracks the apparent offset of the AGN having 105 Mbh/M 0.5 × 108. 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 Mbh-Msph,∗ relation defined by the S´ersic 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 (<105M ), and the new steep (black hole)-(nuclear star cluster) relation, Mbh ∝ M2.7±0.7 nc , are also discussed.