NEAR-INFRARED AND MILLIMETER-WAVELENGTH OBSERVATIONS OF Mol 160: A MASSIVE YOUNG PROTOSTELLAR CORE

We have discovered two compact sources of shocked H2 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 ≥1024 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 the Combined Array for Research in Millimeter-wave Astronomy (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 CH3OH J = 8→7 Class I maser emission from several locations within the core. Comparison with previous observations of 44 GHz CH3OH maser emission shows that 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.