HIGH-VELOCITY MOLECULAR GAS ASSOCIATED WITH COLD IRAS SOURCES

Maps are presented in the J = 2-1 transition of CO for five molecular outflows associated with deeply embedded far-infrared sources. All of the outflows display lobes of both red- and blue-shifted gas with full velocity extents ranging from 37 to 63 km s-1. At least two of the outflows are bipolar but neither is well-collimated. High-velocity 13CO emission is detected in all sources. The data are used to estimate the optical depths, excitation temperatures, masses, momentum supply rates, and energy supply rates for the outflows. A comparison between the properties of IRAS-selected and optically selected molecular outflows is made. We find that the IRAS-selected outflows have significantly greater velocity extents and masses, and hence greater momenta and energies, than their optically selected counterparts when outflows with driving sources of similar luminosities are compared. However, the lobe sizes and dynamical lifetimes of the outflows do not show significant variation between these two samples. The results of this comparison can be understood in the context of a simple model for molecular outflows where local conditions determine the outflow size and the molecular gas decelerates and/or the wind breaks out of the cloud as the outflow evolves.