We have discovered two compact sources of shocked H 2 2.12-µm emission coincident with Mol 160 (IRAS 23385+6053), a massive star-forming core thought to be a precursor to an ultracompact H II region. The 2.12-µm sources lie within 2 (0.05 pc) of a millimeter-wavelength continuum peak where the column density is ≥ 10 24 cm −2 . We estimate that the ratio of molecular hydrogen luminosity to bolometric luminosity is > 0.2%, indicating a high ratio of mechanical to radiant luminosity. CS J=2→1 and HCO + J=1→0 observations with CARMA indicate that the protostellar molecular core has a peculiar velocity of ∼ 2 km s −1 with respect to its parent molecular cloud. We also observed 95 GHz CH 3 OH J=8→7 Class I maser emission from several locations within the core. Comparison with previous observations of 44-GHz CH 3 OH maser emission shows the maser sources have a high mean ratio of 95-GHz to 44-GHz intensity. Our observations strengthen the case that Mol 160 (IRAS 23385+6053) is a rapidly accreting massive protostellar system in a very early phase of its evolution.

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We present the results of a narrow-band near-infrared imaging survey for Molecular Hydrogen emission-line Objects (MHOs) toward 26 regions containing high-mass protostellar candidates and massive molecular outflows. We have detected a total of 236 MHOs, 156 of which are new detections, in 22 out of the 26 regions. We use H 2 2.12-µm/H 2 2.25-µm flux ratios, together with morphology, to separate the signatures of fluorescence associated with photodissociation regions (PDRs) from shocks associated with outflows in order to identify the MHOs. PDRs have typical low flux ratios of ∼ 1.5 -3, while the vast majority of MHOs display flux ratios typical of C-type shocks (∼ 6-20). A few MHOs exhibit flux ratios consistent with expected values for J-type shocks (∼ 3-4), but these are located in regions that may be contaminated with fluorescent emission. Some previously reported MHOs have low flux ratios, and are likely parts of PDRs rather than shocks indicative of outflows. We identify a total of 36 outflows across the 22 target regions where MHOs were detected. In over half these regions, MHO arrangements and fluorescent structures trace features present in CO outflow maps, suggesting the CO emission traces a combination of dynamical effects, which may include gas entrained in expanding PDRs as well as bipolar outflows. Where possible, we link MHO complexes to distinct outflows and identify candidate driving sources.

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