SiO Observations of the NGC 1333 IRAS 2A Protostellar Jet

We present 86.8 GHz SiO J=2-1 observations of the molecular outflow from the protostellar source NGC 1333 IRAS 2A. Silicon monoxide is a sensitive tracer of shocks in molecular gas, and the emission clearly traces terminal bowshocks at the ends of the outflow lobes, as well as emission knots and a source coincident with the protostar. Our three-field mosaic from the BIMA interferometer covers the entire outflow length, including both lobes. The most prominent emission feature, the eastern bowshock, shows SiO at the leading edge, clearly displaced from the maximum seen in CO. This is in contrast to recent observations by Chandler & Richer (2001) of the HH 211 jet, where SiO traced primarily internal working surfaces and was less extended than the CO. Our results are consistent with prompt entrainment at the leading edge of the IRAS 2A bowshocks.