PROBING THE CORE OF CEPHEUS-A - MILLIMETER AND SUBMILLIMETER OBSERVATIONS

We present moderate and high angular resolution (40"-7") maps of the core of the Cepheus A star-forming region using CS J = 3-2 and J = 7-6 emission, which traces the dense gas component of the cloud core, and using far-infrared (450 and 800-mu-m) continuum emission tracing the warm dust component. Three regimes in the core are traced by these observations: (1) a small (approximately 0.14 pc), nearly circular central core of high density (1-10 x 10(6) cm-3) and temperature (30-100 K) containing at least 25% of the mass and which contains the active early-type star formation, (2) an extended (0.5 x 0.25 pc), NE-SW oriented core of mass 200-300 M., temperature 30-40 K, and average density n(H2) approximately 10(5) cm-3 and which, together with the central core, contains 60%-80% of the total core mass, and (3) an extended core envelope of dimensions 0.5 x 0.85 pc oriented primarily north-south, and at a lower density (> 10(4) cm-3). The velocity structure of the core suggests that it is being disrupted by the high-velocity winds driving the molecular outflow and is not due to a rotating circumstellar disk. Although NH3 (J, K) = (1, 1) emission is more easily excited at lower densities than CS and HCN, the previously reported NH3 emitting region is considerably smaller than that traced by either of the other two molecules, indicating that the abundance of ammonia must be significantly lower than expected.