H2 emission from Herbig-Haro objects

Molecular hydrogen emission lines have been detected in six Herbig-Haro objects. The line intensities suggest that the H2 emission arises in a moderate-density, shock-heated gas, consistent with evidence for a similar origin of the visible emission-line spectra in Herbig-Haro objects. Indirect arguments indicate that the typical H2 line widths are less than 70 km/sec and that typical heliocentric radial velocities are no more than 30 km/sec in magnitude.