Olle Morell helped in carrying out some of the spectroscopic observations and Magnus Selhammar in the analysis of the results. Nils Ryde is thanked for checking the calculations and for giving valuable comments on the manuscript and Hugo Schwarz for valuable suggestions and active participation in following up this work with imaging observations. Harm Habing is also thanked for valuable comments on the manuscript. Financial support from the Swedish Natural Science Research Council is acknowledged.
© European Southern Observatory (ESO) 1997
Online publication: July 8, 1998