THE UNUSUAL X-RAY COLLISION MORPHOLOGY OF NGC-4782 4783 (3C-278)/

Deep ROSAT HRI (High-Resolution Imager) imaging of the X-ray-emitting gas associated with the colliding elliptical galaxy pair NGC 4782/4783 reveals for the first time the complexity of the hot gas distribution in a pair of close interacting galaxies. The HRI image of NGC 4782/47 83 shows hot gas around each galaxy, a high surface brightness X-ray b ridge connecting the galaxy pair, tidal-like tails emerging from the t wo galaxies, and a sheet of gas at the interaction interface between t he two galaxies. The hot gas distributions do not peak at the optical centers of the galaxies but are displaced in the same sense as the tid al distensions seen in the optical luminosity distributions. All of th ese remarkable features show the complexity of structure that develops in the hot gas distribution when both hydrodynamical and tidal forces come into play during collisions between ellipticals with hot gas com ponents. Models by Borne and Colina of the bent two-sided radio jet 3C 278 (associated with NGC 4782) indicated that there must be a strong interaction between the hot gas components of NGC 4782/4783 and that t he deflection of the radio jets is likely caused by the ram pressure e xerted on the jet plasma by the hot gas associated with the passing co mpanion NGC 4783. These conclusions are qualitatively confirmed by the HRI image and substantiate the major role played by the hot interstel lar medium, and its asymmetries, in the propagation and entrainment of radio jets in colliding radio host ellipticals.