HIGH-VELOCITY GAS IN POWERFUL RADIO GALAXIES

Components of high-velocity gas have been discovered in the extended emission line regions around two powerful radio galaxies. The velocity shifts - up to -1800 km s-1 relative to systemic in the case of 3C405 (Cygnus A) and up to +1600 km s-1 in the case of 3C265 - are among the largest yet recorded in the extended regions around radio galaxies. In both objects the shifted components appear to have relatively high ionization states - similar to, or higher than, the unshifted components of extended ionized gas. The nature of the acceleration mechanism is currently unclear, but it appears most likely that the large velocity shifts are extreme manifestations of the activity - perhaps the result of interactions between the radio plasma and the warm or hot interstellar medium.