EVOLUTION OF GAS AND STARS IN THE MERGER GALAXY NGC-1316 (FORNAX-A)

We present optical and archival X-ray data on the disturbed-morphology radio elliptical galaxy NGC 1316 (Fornax A), which displays numerous low surface brightness shells, loops, and tails. An extended (81'' x 2 7'', or 9 kpc x 3 kpc) emission-line region (EELR) at a projected dist ance of 35 kpc from the nucleus has been discovered in an approximatel y 90 kpc x 35 kpc, 3.0 x 10(9) L-B. tidal tail. The position and extre me size of the EELR suggest that it is related to the merger process. We suggest that the ionization mechanism of the EELR is shock excitati on and that the gas is a remnant from the merger progenitor. X-ray emi ssion is detected near two tidal tails. Hot, similar to 5 x 10(6) K, g as is probably the predominant gas component in the tidal-tail interst ellar medium. However, based on the current tidal-tail (cold + warm hot) gas mass, a large fraction of the progenitor gas may already resi de in the nucleus of NGC 1316. The numerous and varied tidal-tail syst em suggests that a disk-disk or disk-E merger could have taken place g reater than or equal to 1 Gyr ago, while a low-mass, gas-rich galaxy w ould have started to merge similar to 0.5 Gyr ago.