A search for molecular outflows toward the pre-main-sequence objects

A search for molecular outflows has been conducted toward a sample of 71 young stellar objects dominated by optically selected pre-main-sequence stars. Molecular outflows ranging in size from 0.07 to about 5 pc, with expansion velocities from 6 to 60 km/s, have been detected toward 20 of these objects and in an additional six infrared objects not included in the original survey. The apparent ages of the outflows are from 1000 to 500,000 yr; about half of the observed outflows are bipolar, with the rest showing a wide variety of morphologies. It is found that outflows driven by low-luminosity objects tend to be more bipolar than those driven by high-luminosity objects. The implications of the results of the study are discussed.