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We have obtained K-band spectra at R~5,000 and angular resolution 0.3" of asection of the Herbig-Haro 7 (HH7) bow shock, using the Near-Infrared IntegralField Spectrograph at Gemini North. Present in the portion of the data cubecorresponding to the brightest part of the bow shock are emission lines of H2with upper state energies ranging from ~6,000 K up to the dissociation energyof H2, ~50,000 K. Because of low signal-to-noise ratios, the highest excitationlines cannot be easily seen elsewhere in the observed region. However,excitation temperatures, measured throughout much of the observed region usinglines from levels as high as 25,000 K, are a strong function of upper levelenergy, indicating that the very highest levels are populated throughout. Thelevel populations in the brightest region are well fit by a two-temperaturemodel, with 98.5% of the emitting gas at T=1800 K and 1.5% at T=5200 K. Thebulk of the H2 line emission in HH7, from the 1,800 K gas, has previously beenwell modeled by a continuous shock, but the 5,200 K component is inconsistentwith standalone standard continuous shock models. We discuss various possibleorigins for the hot component and suggest that this component is H2 newlyreformed on dust grains and then ejected from them, presumably followingdissociation of some of the H2 by the shock.

Highly Excited H2 in Herbig-Haro 7: Formation Pumping in Shocked Molecular Gas?