NEUTRAL WINDS FROM PROTOSTARS

We present Arecibo 21 cm line observations of neutral winds associated with young stellar objects. We confirm the detection of fast neutral winds in HH 7 - 11 and in L 1 55 1. These two winds have been coarsely mapped along the CO outflow direction. For the case of HH 7 - 11, we find that the maximum velocity declines from 170 km s-1 at the center (SVS 13), to - 13 5 km s - 1 at a position displaced half a beam away from the center. This finding is consistent with the idea that the neutral wind is partially resolved by our observations and decelerates away from the source SVS 13. In contrast, the extent of the outflow in the case of L1551 is well resolved by the Arecibo beam and we present a map of the high-velocity H I gas along the red CO lobe. The H I observations of HH 7-11 and L1551 support the picture in which the CO outflow is driven by a fast neutral stellar wind that conserves momentum and drives the observed high-velocity molecular outflows. From the observations, the maximum mass-loss rate (assuming a constant velocity wind) and maximum velocity for HH 7 - 11 are M = 8.8 x 10(-6) M. yr -1 and upsilon - 170 km s -1. For L1551 they are M = 6 x 10(-6) M., yr-1 and upsilon approximately 260 km s-1. The high-velocity H I in L1551 extends up to the end of the CO lobe which means that a substantial fraction of the momentum and energy of the wind must be deposited, possibly through a shock, into the ambient cloud. We find that the high-velocity H I along the red lobe has the characteristic triangular profiles indicative of deceleration. For this object we present a simple model of the process of mass entrainment in the atomic wind which reproduces the intensity and shape of the observed line profiles. High-velocity H I gas was searched and not detected in five more objects: RNO 43, R Mon, NGC 2264, B335, FU Ori. For these objects we obtain upper limits on the atomic high-velocity gas which are not stringent. Therefore, even if no high-velocity H I was detected, the observed molecular outflows could still be driven by massive neutral winds. Finally, the upper limit on the atomic mass in the case of FU Ori sets a limit on the mass-loss rate during the active phase which initiated with the outburst in 1937. Again, this is not a stringent limit because it is still an order of magnitude larger than the mass-loss rates required by current models of FU Ori objects.