# Can a black hole exist without encircling stars? Can a black hole exist without stellar dispersion of a galaxy bulge?

The M–sigma (or M–σ) relation is an empirical correlation between the stellar velocity dispersion σ of a galaxy bulge and the mass M of the supermassive black hole at its center.

https://en.wikipedia.org/wiki/M%E2%80%93sigma_relation

http://iopscience.iop.org/article/10.1086/312840/fulltext/

http://arxiv.org/abs/astro-ph/0007369

The observed $M-\sigma$ relation is usually interpreted to mean that somehow MBHs are able to effect their large-scale environments (i.e. their galaxy as a whole). The growing consensus is that the mechanism of this interaction is via 'Feedback', e.g. This paper by Fabian, or this pop-sci article. It is not interpreted to mean that the stars in the galaxy's bulge are physically orbiting the BH, and the dispersion is directly caused by that orbital velocity.