The high-velocity molecular flows near young stellar objects

Abstract

The results of a search for high-velocity molecular gas associated with star forming molecular clouds are reported. Faint, high-velocity (..delta..V> or approx. =30 km s/sup -1/) /sup 12/CO emission is freqently found near buried infrared sources when sufficiently deep (T/sub rms/ <100 mK) integrations are obtained. In most clouds, the high-velocity gas is observed over an extended area having a typical radius around 10/sup 18/ cm and exhibits bipolar structure with the redshifted emission formed in a different region from the corresponding blueshifted emission. The ratio of the flow major and minor diameters varies from about 6 to less than 2, with most sources in the range between 2 and 3, indicating that most flows are not highly collimated. In many sources, the red portion of the line wings is stronger and/or covers a larger angular region of the sky than the corresponding blue wing. The opacity of the /sup 12/CO line wings appears to be greater than unity. Correlations between the central source luminosity and both the flow mechanical luminosity and momentum flux are found. A correlation between the mass of a flow and its apparent size suggests that the flows may be located in molecular clouds with steeplymore » decreasing radial density gradients. The presence of high-velocity outflow in molecular clouds indicates an unanticipated phase of energetic mass loss associated with the birth and early evolution of stars. Even though the flows have large energies, momenta, and a high birthrate, they may not be capable of supporting molecular clouds against free-fall gravitational collapse.« less