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

A field of ~38'x38' around the supernova remnant (SNR) G349.7+0.2 has beensurveyed in the CO J=1-0 transition with the 12 Meter Telescope of the NRAO,using the On-The-Fly technique. The resolution of the observations is 54". Wehave found that this remnant is interacting with a small CO cloud which, inturn, is part of a much larger molecular complex, which we call the ``Large COShell''. The Large CO Shell has a diameter of about 100 pc, an H_2 mass of930,000 solar masses, and a density of 35 cm-3. We investigate the origin ofthis structure and suggest that an old supernova explosion ocurred about 4million years ago, as a suitable hypothesis. Analyzing the interaction betweenG349.7+0.2 and the Large CO Shell, it is possible to determine that the shockfront currently driven into the molecular gas is a non-dissociative shock(C-type), in agreement with the presence of OH 1720 MHz masers. The positionaland kinematical coincidence among one of the CO clouds that constitute theLarge CO Shell, an IRAS point-like source and an ultracompact H II region,indicate the presence of a recently formed star. We suggest that the formationof this star was triggered during the expansion of the Large CO Shell, andsuggest the possibility that the same expansion also created the progenitorstar of G349.7+0.2. The Large CO Shell would then be one of the fewobservational examples of supernova-induced star formation.Comment: accepted in Astronomical Journal, corrected typo in the abstract (in first line, 38' instead of 38"