Hot gas in elliptical galaxies and the formation of head-tail radio sources

Abstract

Elliptical galaxies moving through clusters seem likely to retain a significant interstellar medium (ISM). A simple estimate gives this region a characteristic radius of about 10 kpc. Within this radius the influence of the ISM must be included in any model of radio source structure. Since this scale is similar to that of the small-scale structure now being seen in head-tail radio sources, it suggests that the interstellar medium may be important in the formation of these sources. An alternative model of head-tail sources is suggested in which nonrelativistic or mildly relativistic beams are deflected by transverse pressure gradients induced within the interstellar medium by the galactic motion. It is further suggested that the large-scale structure of a tailed source may be energized by turbulence in the galactic wake.