HIGH-VELOCITY HOT AMMONIA IN BIPOLAR OUTFLOWS

We have detected high-velocity ammonia emission associated with four b ipolar molecular outflows excited by young stars (L1157, L1448, IRAS 3 282, and NGC 2071). The high-velocity emission is more prominent in th e (3, 3) line, although it is also detected in the (1, 1), (2, 2), and (4, 4) lines. We deduce that the accelerated gas is heated to more th an 50-100 K, i.e., a factor of 3-7 over the ambient temperatures (whic h are in the range 12-26 K). Such temperatures, when taken into accoun t in the analysis of previous SiO observations, confirm that the shock ed material is rather dense [n(H-2) approximately 10(5) cm-3]. The NH3 (3, 3) lines, similarly to the SiO emission, arise from shocked mater ial placed along highly-collimated jets or at the lobe ends, and are t hus better understood in the frame of jet-driven models for bipolar ou tflows.