H2 emission in molecular clouds

By observation in the 2μ lines of vibrationally excited H2, H2 emission near a variety of types of very young objects in the DR21/W75, NGC 7538, OMC-2, NGC 6334 and NGC 1999(HH2) molecular clouds has been detected. The observed v = 1-0 S(1) line luminosities (uncorrected for extinction) range from 0.006 L to 2 L solar luminosity. The observations in the 12CO(J = 1-0) line (lambda = 2.6 mm) indicate that all the H2 emission sources, with the exception of the Herbig Haro Object Number 2, are associated with enhanced high velocity wing emission (V/sub hv/ ca 7-20 km sec-1) indicative of very supersonic gas flows. For most of the sources, the energy (ca 1046 - 1047 ergs sec-1) and the momentum (ca 1041 g cm s-1) observed in the high velocity gas are sufficient to account for the unreddened luminosity of the H2 emission under the assumption of shock excitation. It is found that the line ratios in DR21/H2 are inconsistent with pure ultraviolet excitation and derive an excitation temperature of 17000K +- 11000K. It is shown that the region of broad wing emission in DR21 is more compact than originally reported by Dickel et al. (1978) and that the H2 emission region lies just outside the half power radius of the blue-wing emission