2015ApJ...798...54G

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, *_). However, dramatic revisions to the M_bh-M_sph, *_ and M_bh-L_sphrelations, based on samples containing predominantly inactive galaxies, have recently identified a new steeper relation at M_bh ≲ (2-10)x10⁸ M_☉, roughly corresponding to M_sph, *_ ≲ (0.3-1)x10¹¹ M_☉. We show that this steeper, quadratic-like M_bh-M_sph, *_relation defined by the Sérsic galaxies, i.e., galaxies without partially depleted cores, roughly tracks the apparent offset of the AGN having 10⁵ ≲ M_bh/M_☉ ≲ 0.5x10⁸. 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, *_ relation defined by the Sérsic 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 (<10⁵ M_☉), and the new steep (black hole)-(nuclear star cluster) relation, M_bh ∝ M_nc^2.7±0.7, are also discussed.