The smallest and largest black holes seem to be able to move away from the center of gravity in small scale Nebula and even in Galaxies!!
see: Monster colliding black holes might lurk on the edge of spiral galaxies.
see: https://phys.org/news/2017-10-monster-colliding-black-holes-lurk.html
The Contribution Of Outer HI Disks To The Merging Binary Black Hole Population https://arxiv.org/abs/1710.09407
We find that outer HI disks contribute at least as much as dwarf galaxies do to the observed LIGO/Virgo detection rates. see also: https://www.researchgate.net/publication/321098390_The_Einstein_Cross_Lensing_Effect_2_explained_by_the_Quadruple_Dark_Matter_formation_process_of_Edge-On_Spiral_Galaxies_according_to_Quantum_FFF_Theory
