Abstract
Observations of C100α and C125α atomic carbon recombination lines were made at the Algonquin Radio Observatory, towards the neutral interface separating theHii region DR21 (at RA=20h37m14s, Dec=+42°09′00″) from its associated molecular cloud. An analysis of the Cnα observations in conjunction with a simple model of a neutral interface enabled the derivation of the following parameters: electron density of 300 cm−3, electron temperature of 30 K, microturbulent velocity of 2.3 km s−1, and depth of the neutral interface of 0.01 pc. A single,stimulated emission model is sufficient to reproduce the Cnα observations in the wavelength range from λ4.6 cm (C100α) to λ21 cm (C166α). All the known Cnα data do support a pressure equilibrium between the neutral interface and theHii region, after the usual allowance is made for carbon depletion on grains.
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Vallée, J.P. The neutral interface adjoining theHII region DR21. Astrophys Space Sci 129, 339–351 (1987). https://doi.org/10.1007/BF00642652
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DOI: https://doi.org/10.1007/BF00642652