A study of H2 emission in the bipolar proto-planetary nebula IRAS 17150-3224

H-2 emission has been detected in the bipolar proto - planetary nebula IRAS 17150 - 3224 from the 1 - 0 S( 1), 1 - 0 S( 0), and 2 - 1 S( 1) transitions in the 2 mu m region. Line ratios suggest that this emission is due to collisional excitation. High-resolution imaging with NICMOS on HST shows that the emission comes from four regions: clumps near the ends of the lobes ( the brightest region), the lobes in general, a particular region outside the northwest lobe, and a faint loop in the equatorial region. Spatially resolved high-resolution spectra at 2.12 mu m reveal that the H-2 1 - 0 S( 1) line has a velocity width of about 35 km s(-1) in the lobes, consistent with C-type shocks. The emission from the clumps in the lobes appears to arise from the impact of a fast wind with the slower moving material in the AGB wind.