Chown, M. P.; Beckman, J. E.; Cronin, N. J. and White, G. J.
(1982). The M(17)SW molecular source - internally or externally heated?
In: Beckman, J. E. and Phillips, J. P. eds.
Submillimetre Wave Astronomy.
Cambridge: Cambridge University Press, pp. 159–165.
From a measurement of the J = 3→2 rotational emission line of hydrogen isocyanide, and a literature value for that J = 1→0 line (Snell, 1979), the excitation parameters for HNC in the direction of the molecular peak as determined by CO were derived. Kinetic temperatures for the optically thick CO and 13CO transitions are ~ 50 K, while that pertaining to HNC line formation is between 20 K and 5 K. The inference that the central temperature of the cloud is lower than that of its surface supports models in which the cloud is heated not from within, but by the O-B association to the northwest.
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