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 bow-shocks 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. 1. Summary The class 0 source IRAS 2A drives an unusual, highly collimated jet-like outflow first studied in CO (Sandell et al. 1994). Such a young, symmetric, and focused outflow provides an excellent opportunity to observe the expected bow shock of a jet interacting with the molecular ambient gas. We used the BIMA interferometer to map this outflow in SiO in order to trace shocks within the outflow. Our initial three-field, C-array (10 " ×7 ′′ beam) mosaic covers the positions of IRAS 2A and the east and west bow shocks. In addition to this outflow of roughly E-W orientation, a larger, less collimated bipolar outflow originates from nearly the same position (Liseau et al. 1988), and is possibly associated with the nearby source IRAS 2C (Knee & Sandell 2000; Sandell & Knee 2001). Because the position of IRAS 2C agrees poorly with