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Issue A&A
Volume 381, Number 1, January I 2002
Page(s) L33 - L36
Section Letters
DOI http://dx.doi.org/10.1051/0004-6361:20011603



A&A 381, L33-L36 (2002)
DOI: 10.1051/0004-6361:20011603

Letter

Possible evidence for shocks in hot cores

J. Hatchell1 and S. Viti2

1  Max-Planck-Institut für Radioastronomie, Auf dem Hügel 69, 53121 Bonn, Germany
2  Department of Physics & Astronomy, University College London, London WC1E 6BT, UK

(Received 22 October 2001 / Accepted 12 November 2001)

Abstract
The NS/CS ratio can be used to test if shocks or thermal evaporation remove grain ices during massive star formation. The two scenarios lead to differences in the subsequent chemistry: in particular, timescales are shorter if shocks are present. We have measured NS/CS ratios in six hot core sources through observation of high excitation NS, N 34S, C 34S and C 33S with the JCMT. The NS/CS ratios we find are low, $0.02\hbox{--}0.05$, and surprisingly consistent between sources. Comparing with the models of Viti et al. (2001), these values rule out the standard assumption of instantaneous thermal evaporation, and favour a scenario in which hot cores are shocked at an early stage with all grain mantles evaporating instantaneously.


Key words: stars: formation -- molecular processes -- ISM: abundances -- HII regions -- ISM: molecules

Offprint request: J. Hatchell, hatchell@mpifr-bonn.mpg.de

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