Hopkins Ultraviolet Telescope Observations of H2Emission from HH 2

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Abstract
The Hopkins Ultraviolet Telescope spectrum of HH 2 shows Lyman band emission below 1200 Å, and it reveals H2 bands in the quasi-continuum at longer wavelengths. The H2 emission could arise either from Lyα fluorescence (as in other HH objects) or from collisional excitation by hot electrons. The fluorescence hypothesis encounters some difficulty in explaining the lack of individual strong features, while the collisional hypothesis must explain the mixing of hot electrons into the molecular gas before photoionization or collisions with H atoms dissociate the molecules. The spectrum also provides a stringent upper limit to the O VI flux. The upper limit appears to conflict badly with the predictions of bow-shock models that match the observed line widths of HH 2A' and HH 2H.
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