The circumstellar structure and excitation effects around the massive protostar Cepheus A HW 2

Abstract

We report SMA 335 GHz continuum observations with angular resolution of similar to 0.3'', together with VLA ammonia observations with similar to 1'' resolution toward Cep A HW 2. We find that the flattened disk structure of the dust emission observed by Patel et al. is preserved at the 0.3'' scale, showing an elongated structure of similar to 0.6'' size (450 AU) peaking on HW 2. In addition, two ammonia cores are observed, one associated with a hot core previously reported and an elongated core with a double peak separated by similar to 1.3'', with signs of heating at the inner edges of the gas facing HW 2. The double-peaked ammonia structure, as well as the double-peaked CH3CN structure reported previously (and proposed to be two independent hot cores), surround both the dust emission as well as the double-peaked SO2 disk structure found by Jimenez-Serra et al. All these results argue against the interpretation of the elongated dust-gas structure as due to a chance superposition of different cores; instead, they imply that it is physically related to the central massive object within a "disk-protostar-jet" system.