The (black hole)-bulge mass scaling relation at low masses

الأصل · EN

Several recent papers have reported on the occurrence of active galactic nuclei (AGN) containing under-massive black holes relative to a linear scaling relation between black hole mass (Mbh) and host spheroid stellar mass (Mₛph,*). Dramatic revisions to the Mbh-Mₛph,* and Mbh-Lₛph relations, based on samples containing predominantly inactive galaxies, have however recently identified a new steeper relation at Mbh < (2-10)x10⁸ Mₛun, roughly corresponding to Mₛph,* < (0.3-1)x10¹¹ Mₛun. We show that this steeper, quadratic-like Mbh-Mₛph,* relation defined by the Sersic galaxies, i.e. galaxies without partially depleted cores, roughly tracks the apparent offset of the AGN having 10⁵ < Mbh/Mₛun < 0.5x10⁸. That is, these AGN are not randomly offset with low black hole masses, but also follow a steeper (non-linear) relation. As noted by Busch et al., confirmation or rejection of a possible AGN offset from the steeper Mbh-Mₛph,* relation defined by the Sersic galaxies will benefit from improved stellar mass-to-light ratios for the spheroids hosting these AGN. Several implications for formation theories are noted. Furthermore, reasons for possible under- and over-massive black holes, the potential existence of intermediate mass black holes (<10⁵ Mₛun), and the new steep (black hole)--(nuclear star cluster) relation, Mbh (Mₙc)².⁷⁺/⁻⁰.⁷, are also discussed.