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 MBH(sin i)2 = (2.0 ± 0.5) x 109 M⊙ (mbh = 3.2 x 109 M⊙ 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/Lv ≃ 110, significantly strengthening the claim that this mass is due to the presence of a central black hole in M87.