HUBBLE-SPACE-TELESCOPE SPECTROSCOPIC EVIDENCE FOR A 2X10(9) M(CIRCLE-DOT) BLACK-HOLE IN NGC-3115

The discovery by Kormendy & Richstone of an M(.) similar or equal to 1 0(9) M(.) massive dark object (MDO) in NGC 3115 is confirmed with high er resolution spectroscopy from the Canada-France-Hawaii Telescope (CF HT) and the Hubble Space Telescope (HST). Measurements with the CFHT a nd Subarcsecond Imaging Spectrograph improve the resolution from sigma = 0''.44 to sigma* = 0''.244 (sigma* = Gaussian dispersion radius of the point-spread function). The apparent central velocity dispersion rises from sigma = 295 +/- 9 km s(-1) to sigma = 343 +/- 19 km s(-1). The Faint Object Spectrograph and COSTAR-corrected HST provide a furth er improvement in resolution using a 0''.21 aperture. Then, the measur ed sigma = 443 +/- 18 km s(-1) is remarkably high, and the wings of th e velocity profiles extend beyond 1200 km s(-1) from the line centers. Similarly, the apparent rotation curve rises much more rapidly than i s observed from the ground. Published dynamical models fit the new obs ervations reasonably well when ''observed'' at the improved spatial re solution; V and sigma are at the high end of the predicted range near the center. Therefore, M(.) > 10(9) M(.). The spatial resolution has n ow improved by a factor of similar to 5 since the discovery observatio ns, and the case for a central MDO has strengthened correspondingly. W ith HST and the Second Wide Field and Planetary Camera, NGC 3115 also shows a bright nucleus. This is very prominent and distinct from the b ulge when the superposed nuclear disk is subtracted. After bulge subtr action, the nucleus has sigma = 600 +/- 37 km s(-1), the largest centr al dispersion seen in any galaxy. If the nucleus contained only old st ars and not an MDO, its escape velocity would be similar to 352 km s(- 1), much smaller than the observed velocities of the stars. This is in dependent proof that an MDO is present. The new observations put more stringent constraints on the radius inside which the dark mass lies an d strengthen the case that it is a 2 x 10(9) M(.) black hole.