Is there really a supermassive black hole in M87?

Abstract

We present the first HST long-slit spectrum of a gaseous disc around a candidate supermassive black hole. The results of this study on the kinematics of the gaseous disc in M87 are a considerable improvement in both spatial resolution and accuracy over previous observations, and require a projected mass of M_BH(sin i)² = (2.0±0.5)×10⁹M_sun (M_BH = 3.2×10⁹M_sun for a disc inclination i = 52°) concentrated within a sphere of radius less than 0.05 arcsec (3.5 pc) to explain the observed rotation curve. The kinematics of the ionized gas are well described by a thin disc in Keplerian motion. A lower limit to the mass-to-light ratio of this region is M/L_V ≅ 110, significantly strengthening the claim that this mass is due to the presence of a central black hole in M87.