Molecular Line Observations of the S235B Region

Abstract The core of the molecular cloud associated with the young stellar object S235B has been observed in molecular lines of CS, CO, and CH3OH with high angular resolution by the 45-m radio telescope of the Nobeyama Radio Observatory. The core is 0.6 × 1.0 pc in extent. The number density of molecular hydrogen and the fractional abundance of CS relative to molecular hydrogen are estimated to be ~3×105cm−3 and ~5×10−10, respectively. Our CO observations show evidence of the bipolar flow. This suggests that S235B is not a compact H ii region, but an expanding ionized envelope around a young star. The mass-loss rate from S235B is estimated as ~ 10−6M◉ yr−1. CHSOH emission shows a very compact distribution and a narrow line width, suggesting that the methanol lines are weakly masing.