Neutral stellar winds that drive bipolar outflows in low-mass protostars

Abstract

Using the Arecibo radio telescope at the 21 cm line of atomic hydrogen, the authors detected a neutral atomic wind in the bipolar flow source HH 7-11. The H I gas reaches velocities up to ≡170 km s<SUP>-1</SUP> and has an associated mass-loss rate from the protostar of ≡3×10<SUP>-6</SUP>M_sun;yr<SUP>-1</SUP>, which suffices to drive the observed CO bipolar flow. The 21 cm line profile indicates the H I wind to be decelerating. The deceleration of the atomic wind may arise from interaction with the surrounding molecular cloud. Evidence exists that ambient molecular material has been entrained in the decelerating H I wind.At the Nobeyama 45 m telescope the authors detected HCO<SUP>+</SUP> at velocities intermediate between the H I wind and the CO bipolar outflow. The authors also discuss more ambiguous evidence in H I and in OH for a decelerating neutral stellar wind from L1551 IRS 5.