Abstract
We present new upper limits for black hole masses in extremely late type spiral galaxies. We confirm that this class of galaxies has black holes with masses less than 106M⊙, if any. We also derive new upper limits for nuclear star cluster masses in massive galaxies with previously determined black hole masses. We use the newly derived upper limits and a literature compilation to study the low mass end of the global-to-nucleus relations. We find the following. (1) TheMBH-σrelation cannot flatten at low masses, but may steepen. (2) TheMBH-Mbulgerelation may well flatten in contrast. (3) TheMBH-Sersicnrelation is able to account for the large scatter in black hole masses in low-mass disk galaxies. Outliers in theMBH-Sersicnrelation seem to be dwarf elliptical galaxies. When plottingMBHversusMNCwe find three different regimes: (a) nuclear cluster dominated nuclei, (b) a transition region, and (c) black hole-dominated nuclei. This is consistent with the picture, in which black holes form inside nuclear clusters with a very low-mass fraction. They subsequently grow much faster than the nuclear cluster, destroying it when the ratioMBH/MNCgrows above 100. Nuclear star clusters may thus be the precursors of massive black holes in galaxy nuclei.
Highlights
Supermassive black holes (BHs) are thought to be ubiquitous in the nuclei of massive galaxies
When plotting MBH versus MNC we find three different regimes: (a) nuclear cluster dominated nuclei, (b) a transition region, and (c) black hole-dominated nuclei
This is consistent with the picture, in which black holes form inside nuclear clusters with a very low-mass fraction
Summary
Supermassive black holes (BHs) are thought to be ubiquitous in the nuclei of massive galaxies. NCs typically have stellar velocity dispersions of 15–35 kms−1, effective radii of a few parsecs, and dynamical masses of ∼106–107 M (B02 [8, 9]). They show stellar populations of multiple ages [10,11,12], pointing towards them having a complex formation history. This might be related to their special location in the galaxy, as on average, NCs appear to sit at the photometric centre of their host galaxy [6, 13]. We recently showed that for bulgeless galaxies their location coincides with the kinematic centre, that is, the bottom of the potential well [14]
Sign-in/Register to view highlights & summary Sign-in/Register to access full text options 
Free) 
Talk to us
Join us for a 30 min session where you can share your feedback and ask us any queries you have
Schedule a call
