Do Supermassive Black Holes Exist at the Center of Galaxies?

Abstract

Models of superdense star clusters at the center of galaxies are investigated to see whether such objects can be stable and long-lived based on evaporation and collision time-scales and stability criteria. We find that physically reasonable models of massive clusters of stellar remnants can exist with masses $\geq 10^6 M_{\odot}$, which could simulate black holes at the center of galaxies with large $M/L$ ratios and gas motions of order $\geq 10^3$ km $s^{-1}$. It follows that the evidence is not conclusive for massive dark objects at the center of galaxies being black holes.

12 pages RevTex. No figures. Revised version with the same conclusions as the original version