High Spectral Resolution Observations of the H 2 2.12 Micron Line in Herbig-Haro Objects

High-spectral-resolution Fabry-Perot observations of the H2 2.12-micron line emissions of several Herbig-Haro (HH) objects are discussed. It is shown that H2 emission by the shock heating of external molecular gas in the wings of the bow shock associated with the working surface of a high-velocity jet may occur for HH objects associated with the jet's end. The shock heating of external molecular gas entrained in the flow by internal shocks occurring in the jet itself and/or in its boundary layer may be the H2 emission mechanism for HH objects observed along the flow axis.