NARROW-BAND HST IMAGES OF M87 - EVIDENCE FOR A DISK OF IONIZED-GAS AROUND A MASSIVE BLACK-HOLE

We present HST WFPC2 narrowband Halpha + [N II] images of M87 which sh ow a small disk of ionized gas with apparent spiral structure surround ing the nucleus of M87. The jet projects approximately 19.-degrees-5 f rom the minor axis of the disk, which suggests that the jet is approxi mately normal to the disk. In a companion Letter, Harms et al. measure radial velocities at r = +/-0''.25 along a line perpendicular to the jet, showing that one side of the disk is approaching at 500 +/- 50 km s-1 and the other side of the disk is receding at 500 +/- 50 km s-1. Absorption associated with the disk and the sense of rotation imply th at the apparent spiral arms trail the rotation. The observed radial ve locities corrected for a 42-degrees inclination of the disk imply rota tion at +/- 750 km s-1. Analysis of velocity measurements at four posi tions near the nucleus gives a total mass of approximately 2.4 +/- 0.7 x 10(9) M(.) within 18 pc of the nucleus, and a mass-to-light ratio ( M/L)I = 170. We conclude that there is a disk of ionized gas feeding a massive black hole in the center of M87.