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Astron. Astrophys. 338, 713-722 (1998)

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Sulphur chemistry and evolution in hot cores

J. Hatchell 1, M.A. Thompson 2, T.J. Millar 1 and G.H. Macdonald 2

1 Department of Physics, UMIST, P.O. Box 88, Manchester M60 1QD, UK
2 Electronic Engineering Laboratory, University of Kent, Canterbury, Kent CT2 7NT, UK

Received 5 June 1998 / Accepted 20 July 1998

Abstract

We compare the results of our JCMT spectral line survey of molecular gas towards ultracompact HII regions with the predictions of models of sulphur chemistry in hot cores. We investigate the range of evolutionary models that are consistent with the observed physical conditions and chemical abundances, and see to what extent it is possible to constrain core ages by comparing abundances with the predictions of chemical models. The observed abundance ratios vary little from source to source, suggesting that all the sources are at a similar evolutionary stage. The models are capable of predicting the observed abundances of H2S, SO, SO2, and CS. The models fail to predict the amount of OCS observed, suggesting that an alternative formation route is required. An initial H2S abundance from grain mantle evaporation of [FORMULA] is preferred.

Key words: ISM: molecules – ISM: clouds – ISM: HII regions – molecular processes – radio lines: ISM

Send offprint requests to: J. Hatchell

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© European Southern Observatory (ESO) 1998

Online publication: September 14, 1998
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