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Astron. Astrophys. 342, 809-822 (1999)


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A 330-360 GHz spectral survey of G34.3+0.15

III. The outer halo

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

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

Received 25 June 1998 / Accepted 3 November 1998

Abstract

We have undertaken a 330-360 GHz molecular line survey of the halo gas surrounding the hot core associated with G34.26+0.15. In contrast to our molecular line survey of the hot core itself, where 338 lines from at least 38 species were detected, only 18 lines from 9 species were detected in the halo. The lines are mainly single transitions of simple diatomic and triatomic molecules. Lower limits to their column densities have been evaluated by an LTE method. In the case of methanol, where four transitions were detected, the rotation temperature and column density have been evaluated by the rotation diagram technique. We have modified the previous depth-dependent chemical model developed in Paper II to calculate the column densities observed along a general line of sight drawn through the model cloud. The model is also extended to produce beam-averaged column densities for better comparison with those observed. We compare the model column densities with those observed and make recommendations for future depth-dependent chemical modelling of hot cores.

Key words: line: identification – ISM: abundances – ISM: individual objects: G34.3+0.15 – ISM: molecules – radio lines: ISM

Send offprint requests to: G.H. Macdonald

© European Southern Observatory (ESO) 1999

Online publication: February 23, 1999

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