The kinetic temperature gradient and the structure of a thin molecular disk in Cepheus A

With the VLA the (2, 2) inversion transition line of NH3 was observed toward Cepheus A. Five small clumps were detected within the Cep A-1 and Cep A-3 ammonia condensations reported by Torrelles et al. (1983). Cep A-1 and Cep A-3 may be physically connected, thus constituting a very elongated structure with a length-to-width ratio of 13 to 1. The stellar activity center appears embedded within this structure. A comparison between the (2, 2) and (1, 1) ammonia emission reveals heating of the molecular gas close (less than about 3 arcsec) to the activity center. This result supports the interpretation that the knots seen in continuum are bright rims excited by one or two central stars. This is the first time that a direct map of the gas temperature has been obtained with the VLA, reflecting the quality of the system and suggesting the possibility of doing similar studies in other molecular clouds. It is found that the central heating source resides on the northwest face of the ammonia disklike structure. This is in the same direction that the redshifted CO outflow seems to be directed. It is suggested that this orientation of the central source with respect to a dense disk may explain the morphology of the outflow. It is proposed that the dense disk impedes the outflow in the southeast direction, while the outflow expands more freely in the northwest direction. Higher-resolution CO observations of the morphology of the outflow would provide a test for this model. 33 references.