Sub-arcsecond imaging of SiO in the HH 211 protostellar jet

Abstract

We present images of the HH 211 molecular jet in the SiO v=0, J=1-0 line at 43 GHz made with the Very Large Array at approximately 0.5 arcsec resolution. The SiO emission appears to trace primarily internal bowshocks in the outflow, suggesting that the dust and molecular gas are accelerated via prompt entrainment at internal working surfaces in the jet. There is also some evidence for limb-brightening of the SiO emission, indicating that SiO emission may also arise from entrainment in the jet's boundary layer. Excitation temperatures of >~150-200 K are inferred from the SiO emission. Enhancements in the SiO abundance of ~10^6 over interstellar values are observed, and the possible origin of the SiO is discussed.