HIGH-RESOLUTION RADIO OBSERVATIONS OF THE SUPERNOVA REMNANT 3C 391 - POSSIBLE BREAKOUT MORPHOLOGY

We present radio observations of the bright, compact supernova remnant 3C 391 (G31.9 + 0.0), made with the Very Large Array2 at 6'' resoluti on. The remnant's morphology suggests expansion into a medium with a v ery strong density gradient. We interpret radio and x-ray [Wang & Sewa rd, ApJ, 279, 705 (1984)] morphologies as evidence for a breakout of t he expanding material into a region of abruptly lower density. The CO survey of Sanders et al. [ApJS, 60, 1 (1986)], though not fully sample d, shows the presence of molecular gas at the position of the remnant, with a radial velocity of 90-1 10 km s-1, similar to the highest velo city absorption features seen in H I toward 3C 39 1. This gas may thus be near the remnant, though direct evidence of interaction is lacking . More detailed CO observations, and searches for evidence of shocked molecular gas such as 2.12 mu emission from H-2, might confirm or refu te the tantalizing possibility that 3C 391 is interacting with an obse rvable molecular cloud.