We are indebted to Dr. S. Digel for helping in the selection of sources; to F. Azagra for assistance with the data reduction; to A. Luna for help with Fig. 5; and to Dr. E. Churchwell and Dr. T. Megeath for helpful discussions and suggestions. A thorough review by our referee greatly helped to improve the paper. The staff at the SEST and OSO telescopes kindly assisted us within the course of the observations. The Swedish-ESO Submillimetre Telescope is operated jointly by ESO and the Swedish National Facility for Radioastronomy, Onsala Space Observatory, at Chalmers University of Technology. The Onsala 20m telescope is operated by the Swedish National Facility for Radioastronomy, Onsala Space Observatory, at Chalmers University of Technology. L.B. acknowledges support from a Chilean Cátedra Presidencial en Ciencias . J.M., L.B., and S.C. acknowledge support from FONDECYT grant 8970017.
© European Southern Observatory (ESO) 2000
Online publication: June 8, 2000