The detection of a dense swept-up CS shell in the M-0.02-0.07 molecular cloud is reported. The projected shell follows the edge of Sgr A East for almost half its circumference, giving a convincing picture of the compression of the 50 km/s cloud by Sgr A East. Highly Doppler-shifted emission is found just inside this shell, providing kinematic evidence for the acceleration of the molecular gas by the blast wave. The dense core of M-0.02-0.07, located just beyond the advancing compression wave, is as yet unaffected. The compact H II regions A-D are also beyond the reach of the compression wave. They must thus predate the SN explosion, and Sgr A East cannot have precipitated their collapse into the star-formation phase. The compact H II regions must be the result of an earlier episode of massive star formation. Observations of IR fine-structure lines indicate that the excitation of the ionized regions is consistent with the presence of a single O8-O9 star in each of the compact H II regions, and IR extinction arguments suggest that these star formation sites are located close to the front surface of the molecular cloud.
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Serabyn et al. (1992) studied this question.