MOLECULAR-HYDROGEN OBSERVATIONS OF CEPHEUS-A-WEST

The Herbig-Haro complex GGD37 is an active region in the west of Cephe us A. We have used the ISO Short Wavelength Spectrometer (SWS) to inve stigate the physics of this region by observations of molecular hydrog en and forbidden atomic and ionic emission lines over a wide wavelengt h and excitation energy range. We find excitation temperatures of the emitting molecular gas to be between 700 and 11000 K, the former being thermal in nature, whilst the latter implies a contribution from non- thermal processes. Gas densities in the emitting region are at least 1 0(5) cm(-3). An H-2 ortho-to-para ratio of 3, equal to the ratio of st atistical weights, is consistent with our observations. The forbidden transitions can be modelled by a planar J-shock with pre-shock density of 10(3) to 10(4) cm(-3) and velocity 70 to 80 km s(-1). The H-2 line s cannot be fit by either a single planar J- or C-shock, but instead r equire a combination of at least two C-shocks with different pre-shock density, shock velocity and covering factor.