This work was stimulated by an intense discussion of W. H. K. with R. Genzel. We further acknowledge support from the ISO Spectrometer Data Centre at MPE Garching, funded by DARA under grant 50 QI 9402 3, and thank in particular D. Kunze and E. Sturm for their help. The data reduction was performed using the ISO Spectral Analysis Package (ISAP), which is a joint development by the LWS and SWS Instrument Teams and Data Centers. Contributing institutes are CESR, IAS, IPAC, MPE, RAL, and SRON. We acknowledge constructive criticism by the referee Dr. V. Bujarrabal. This work was supported by the Deutsche Zentrum für Luft- und Raumfahrt (DLR) under grant 50 OR 95020.
© European Southern Observatory (ESO) 1999
Online publication: November 3, 1999