A molecular shell with star formation toward the supernova remnant G349.7+0.2

A field of about 38'x38' 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 N RAO, 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 t he "large CO shell." The large CO shell has a diameter of about 100 pc, an H-2 mass of 9.3 x 10(5) M-. and a density of 35 cm(-3). We investigate the origin of this structure and suggest as a suitable hypothesis that an old s upernova explosion occurred about 4x10(6) yr ago. Analyzing the interaction between G349.7+0.2 and the large CO shell, it is possible to determine tha t the shock front currently driven into the molecular gas is a nondissociat ive shock (C-type), in agreement with the presence of OH 1720 MHz masers. T he positional and kinematic coincidence of one of the CO clouds that consti tute 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 t he formation of this star was triggered during the expansion of the large C O shell and suggest the possibility that the same expansion also created th e progenitor star of G349.7+0.2. The large CO shell would then be one of th e few observational examples of supernova-induced star formation.