THE CENTERS OF EARLY-TYPE GALAXIES WITH HST .1. AN OBSERVATIONAL SURVEY

We have obtained V-band images of 45 nearby elliptical galaxies and bu lges using the original Planetary Camera of the Hubble Space Telescope . The majority of the sample is at distances of 10 - 20 Mpc, This repr esents a substantial increase in the number of galaxies that have been studied at a resolution of a few parsecs. At this resolution, many ga laxies reveal previously unknown central disks, dust clouds, and nucle ar components. We find that galaxies have two types of brightness prof iles. The first type consists of galaxies that have cores. These galax ies have brightness profiles that ''break'' from steep outer power law s to shallow inner cusps, The core class includes many galaxies that h ad cores apparently resolved from the ground. The second type consists of galaxies that have profiles that continue into the resolution limi t as steep power laws, showing no evidence of cores of any sort. We th us find that all galaxies studied so far have singular brightness prof iles in the sense that I(r) similar to r(-gamma) as r --> 0.'' 1. With 0 < gamma < 0.3 at the few parsec scale for galaxies with cores, and gamma similar to 1 for power-law galaxies. No galaxies in our sample h ave a central region that is constant in surface brightness, This impl ies that the stellar density in these systems is still increasing stee ply at the HST resolution limit. Many galaxies reach stellar mass dens ities of similar to 5 x 10(4) M. pc(-3) at the resolution limit, appea ring similar in form to M32 at radii of a few parsecs. The con and pow er-law profile classes correspond to the Jaffe et al. [AJ, 108, 1567 ( 1994)] Type I and II profiles; however, we disagree with their suggest ion that the presence of a central stellar disk is closely related to, or even determines, profile type. Power-law galaxies are seen at all ellipticities, and the majority of them show no evidence for central d isks. (C) 1995 American Astronomical Society.