摘要
Observations are recounted addressing the nature of the focusing agent in the phenomenon of bipolar mass outflow in regions of star formation. The (J, K)=(1, 1) inversion transition of ammonia was searched in 10 sources of bipolar outflow, and the emission was detected and mapped in seven of them. The ammonia data show the correlation between internal velocity dispersion and cloud size and mass previously obtained from carbon monoxide observations. The molecular condensations associated with the bipolar outflows are generally elongated and engulf the compact object suspected to be the source of energy of the system. For nine sources where clear orientations could be assigned to both the major axis of the condensation and the direction of the outflow, seven cases were found where the axes were nearly perpendicular. This suggests that these elongated clouds may be toroidal with dimensions of tenths of parsecs and may provide the focusing mechanism in bipolar outflows. In this model, the central object's stellar wind has created a bipolar cavity in an originally pancake-shaped cloud. The wind, which could be isotropic near the star, is stopped in the plane of the dense toroid but escapes along the poles, accelerating the surrounding lower density molecular gas.