We present the first HST long-slit spectrum of a gaseous disk around a candidate super-massive black-hole .
The results of this study on the kinematics of the gaseous disk in M87 are a considerable improvement in both spatial resolution and accuracy over previous observations and requires a projected mass of M _ { \mathrm { BH } } ( \sin i ) ^ { 2 } = ( 2.0 \pm 0.5 ) \mbox { $ \times 10 ^ { 9 } $ } \mbox { $ M _ { % \odot } $ } ( M _ { \mathrm { BH } } = 3.2 \mbox { $ \times 10 ^ { 9 } $ } \mbox { $ M _ { \odot } $ } for a disk inclination i = 52 ^ { \circ } ) concentrated within a sphere whose radius is less than 0 \aas@@fstack { \prime \prime } 05 ( 3.5 pc ) to explain the observed rotation curve .
The kinematics of the ionized gas is well described by a thin disk in keplerian motion .
A lower limit to the mass-to-light ratio of this region is M/L _ { \mathrm { V } } \simeq 110 , significantly strengthening the claim that this mass is due to the presence of a central black-hole in M87 .