HUBBLE-SPACE-TELESCOPE PLANETARY CAMERA IMAGES OF NGC-1316 (FORNAX-A)

We present HST Planetary Camera V and I band images of the central reg ion of the peculiar giant elliptical galaxy NGC 1316. These high resol ution images reveal that the central surface brightness rises sharply to 12.1 mag arcsec(-2) in the I band and 13.5 mag arcsec(-2) in the V band. The inner profile is well fit by a nonisothermal core model with a core radius of 0''.41+/-0''.02 (34 pc). At an assumed distance of 1 6.9 Mpc, the deprojected luminosity density reaches similar to 2.0x10( 3)L(circle dot) pc(-3). Outside the inner two or three arcseconds, a c onstant mass-to-light ratio of similar to 2.2+/-0.2 is found to fit th e observed line width measurements. The line width measurements of the center indicate the existence of either a central dark object of mass 2x10(9)M(circle dot), an increase in the stellar mass-to-light ratio by at least a factor of 2 for the inner few arcseconds, or perhaps inc reasing radial orbit anisotropy towards rile center, The mass-to-light ratio run in the center of NGC 1316 resembles that of many other gian t ellipticals, some of which are known from other evidence to harbor c entral massive dark objects (MDOs). The V-I color of unreddened region s is found to be uniform at 1.55+/-0.10. The profile dots not get sign ificantly bluer near the center as might be expected in a merger, exce pt for perhaps the innermost 0''.1. Fits to the unextinguished regions at the center raise concerns that the possible UV-blight point source reported by Fabbiano et al. [ApJ, 434, 67 (1995)] is partially or ful ly explained by dust clouds wrapped around the central line of sight. The smoothness of the underlying stellar distribution allows analysis of the three-dimensional distribution of the dust. We use two observab les; the color excess and the ratio of observed V band flux to that of a symmetric smooth fit. The maximum optical depth is only A(v) simila r to 1.5, and only complexes on the near side of the galaxy are detect ed. We also examine twenty globular clusters associated with NGC 1316 and report their brightnesses, colors, and limits on tidal radii. The brightest cluster has ii luminosity of 9.9X10(6)L(circle dot) (M(v)=-1 2.7), and the faintest detectable cluster has a luminosity of 2.4X10(5 )L(circle dot) (M(v)=-8.6). The globular clusters are just barely reso lved, but their core radii are too small to be measured. The tidal rad ii in this region appear to be less than or equal to 35 pc. Although t his galaxy seems to have undergone a substantial merger in the recent past, young globular clusters are not detected. (C) 1996 American Astr onomical Society.