MOLECULAR LINE OBSERVATIONS OF THE EXTREMELY HIGH-VELOCITY MOLECULAR-FLOW NEAR HH 7-11

We observed CO J = 2-1 lines of the extremely high velocity (EHV) molecular gas near HH 7-11. The CO J = 2-1 lines may show features which suggest that the EHV gas is clumped. The CO J = 2-1 to J = 1-0 line ratio in the EHV wing implies a large gas density, 103 or 104 cm-3 depending on whether CO molecules are excited by collisions with H2 or H. The results of CO observations are not inconsistent with the interpretation of the EHV CO wing as the emission from CO molecules formed in the neutral stellar wind, which is primarily atomic. However, the implied large gas density suggests that the wind is not homogeneous but blowing in either clumps, filaments, or sheets. We also searched for SiO v = 0, 1 J = 2-1, and SO JK = 22-11 lines toward the EHV gas near HH 7-11. We detected a broad SiO v = 0 J = 2-1 line and barely identified a SO line. The EHV wing was not detected in either line. We obtained an upper limit 0.01 for the abundance ratio SiO/CO in the EHV gas, which is consistent with a chemical model for neutral stellar winds. The SiO line that we detected is possibly originated from the interface between the stellar wind and the ambient medium. There was no SiO maser emission.