HST PLANETARY CAMERA OBSERVATIONS OF \\FORNAX~A
Session 6 -- Normal Galaxies: Structure and Dynamics
Display presentation, Monday, 9:20-6:30, Pauley Room

[6.17] HST PLANETARY CAMERA OBSERVATIONS OF \\FORNAX~A

D.M. Dowling, E.J. Shaya (U of Maryland), E.A. Ajhar, T.R. Lauer (NOAO), S.M. Faber (UCSC)

Planetary Camera images of nearby giant elliptical galaxy Fornax A (NGC 1316) taken with V and I-band filters reveal a central cusp down to $0\asec04$ rather than a core of radius $1\asec04$ as previously reported (Schweizer 1981), however; there is a substantial break in slope at $0\asec9$. The profile in V-magnitudes at radii $> 1^{\prime\prime}$ can be fit by an $r^{1/4}$ law and at the center the deconvolved profile approaches an asymptotic power law slope of 1.4 and reaches $>13.5\ mag/sq~arcsec$ within $0\asec1$. A color of V $-$ I = 1.6 is seen over most of the galaxy. No significant color gradient is seen, thus there is no young stellar population that can account for the low M/L ratio at the center of this galaxy. The cusp cannot be exlained by a significant point mass at the center. Analysis is complicated by the existence of extinction clouds very close to the center. Color analysis reveals parts of the dust lane are substantially forward of center. Filamentary loops of extinction are seen close to the line-of-sight to the center.