Results of high-sensitivity, 4-arcsec-resolution imaging of the thermal ammonia and water maser emission of the DR 21 (OH) molecular cloud are presented. Images of the NH3(1, 1) and 2, 2) transitions show four primary emission regions embedded in a generally clumpy emission distribution. A total of 18 ammonia cores are identified in these images. An analysis of the physical properties of these cores shows that they are massive (15-1000 solar masses) and warm (about 20 to greater than 80 K) with a range of sizes (0.06-0.28 pc). One of these cores is a hot (greater than 80 K), compact (about 0.07 pc) region associated with shell-type H2O maser emission. The 3D distribution of these cores suggests a strong interaction between young massive stars and their maternal environs. Two source concepts are formulated to explain this distribution.
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Mangum et al. (1992) studied this question.