We acknowledge stimulating conversations with R. Bachiller, F. Bertoldi, P. Cox, T. Oliva, M. Perinotto, A. Tielens and M. Walmsley in the long course of preparing this paper. B. Draine kindly ran a version of his PDR code which had a more detailed calculation of H2 line intensities, in order to verify the accuracy of our various approximations for the individual H2 line intensities. Some of this work was done while AN was visiting the astronomy department of the University of California at Berkeley. DJH acknowledges travel support from ASI grants 92-RS-54, 94-RS-152 and 94-RS-152 to the Osservatorio di Arcetri and research support from the NASA Astrophysical Theory Program.
© European Southern Observatory (ESO) 1998
Online publication: August 17, 1998