Black-hole kicks are powerful. I mean, really powerful. They can even eject supermassive black holes from the heavier galaxies in our Universe. And then these galaxies are left “empty”…
Davide Gerosa, Alberto Sesana.
Monthly Notices of the Royal Astronomical Society 446 (2015) 38-55.
arXiv:1405.2072 [astro-ph.GA].