G34.3 + 0.2 - A 'cometary' H II region

Abstract

Radio-frequency observations of the H II complex G34.3 + 0.2 made at 1 arcsec resolution with the VLA indicate a component whose appearance resembles that of a comet, containing an ultracompact H II 'head' and a diffuse 'tail'. This 'cometary' H II region points (from tail through head) in the direction of the supernova remnant W44 which lies at a projected separation of 40 pc. The morphology of the cometary source might be explained as owing to the interaction of a newly formed O type star with a large (40 pc radius) shell. This shell is seen in both CO and H I and may have been driven outward from the center of W44 by a wind from the stellar precursor to the supernova.