The authors would like to thank the JCMT staff for their support during the observations, particularly Iain Coulson for general help and for service observation support; also the referee M. Hogerheijde for constructive comments, and an anonymous referee for suggestions based on an earlier version of this paper. This research was supported by the UK Particle Physics and Astronomy Research Council (PPARC) grant to UMIST. The James Clerk Maxwell Telescope is operated by The Joint Astronomy Centre on behalf of the Particle Physics and Astronomy Research Council of the United Kingdom, the Netherlands Organisation for Scientific Research, and the National Research Council of Canada.
© European Southern Observatory (ESO) 1999
Online publication: March 18, 1999