The interaction between radio lobes and hot gas in the nearby radio galaxies 3 C 285 and 3 C 442 A

We present Chandra observations of two nearby radio galaxies in group environments , 3C 285 and 3C 442A. The host galaxies of both sources are involved in mergers with nearby massive galaxies, and the hot gas in the systems is extended along lines joining the interacting galaxies. Both sources show strong evidence for interactions between the radio lobes and the asymmetrical hot gas. We argue that the structure in the hot gas is independent of the existence of the radio lobes in these systems, and argue that hot gas shaped by an ongoing massive galaxy merger may play an important role in the dynamics of radio lobes in other objects. For 3C 442A, our observations show that gas is being driven out of both members of the host interacting galaxy pair, and the implied constraints on galaxy velocities are consistent with mildly supersonic motions with respect to the group-scale hot gas. The previously known filamentary radio structure in the center of 3C 442A may be a result of the interaction between hot gas expelled from these galaxies and pre-existing radio-emitting plasma. In 3C 285, where there is no ongoing galaxy merger, the powerful radio source is probably having a significant effect on the energetics of the host group.