SYNTHESIS IMAGING OF THE DR 21 (OH) CLUSTER .2. THERMAL AMMONIA AND WATER MASER EMISSION

High-sensitivity, 4" resolution images of the thermal ammonia and water maser emission have been made of the DR 21 (OH) molecular cloud. 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 has shown that they are massive (M(G) congruent-to 15-1000 M.) and warm (T(K) congruent-to 20 to greater than 80 K) with a range of sizes (theta(S) congruent-to 0.06-0.28 pc). One of these cores is a hot (T(K) > 80 K), compact (theta(S) congruent-to 0.07 pc) region associated with shell-type H2O maser emission. The three-dimensional 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. Analysis of the observed distribution of NH3 core mass shows that the mass spectrum follows a power law, dN/dM is-proportional-to M(-alpha), with alpha greater-than-or-similar-to 0.7, consistent with previous determinations. A comparison between the viral masses in Taurus, OMC 1/OMC 2, and DR 21 (OH) has been made. OMC 1/OMC 2 and DR 21 (OH) have similar star-forming core properties, which are very different from those found in Taurus. Core virial masses seems to represent a fundamental distinction between low- and high-mass star formation.