A Molecular Shell with Star Formation toward the Supernova Remnant G349.7+0.2

Abstract

A field of about 38' × 38' around the supernova remnant (SNR) G349.7+0.2 has been surveyed in the CO J = 1–0 transition with the 12 m telescope of the NRAO, using the on-the-fly technique. The resolution of the observations is 54''. We have found that this remnant is interacting with a small CO cloud, which, in turn, is part of a much larger molecular complex, which we call the CO shell. The large CO shell has a diameter of about 100 pc, an H2 mass of 9.3 × 105 M⊙, and a density of 35 cm-3. We investigate the origin of this structure and suggest as a suitable hypothesis that an old supernova explosion occurred about 4 × 106 yr ago. Analyzing the interaction between G349.7+0.2 and the large CO shell, it is possible to determine that the shock front currently driven into the molecular gas is a nondissociative shock (C-type), in agreement with the presence of OH 1720 MHz masers. The positional and kinematic coincidence of one of the CO clouds that constitute the large CO shell, an IRAS pointlike source, and an ultracompact H II region indicates the presence of a recently formed star. We suggest that the formation of this star was triggered during the expansion of the large CO shell and suggest the possibility that the same expansion also created the progenitor star of G349.7+0.2. The large CO shell would then be one of the few observational examples of supernova-induced star formation.