MOLECULAR OUTFLOWS ASSOCIATED WITH A FLUX-LIMITED SAMPLE OF BRIGHT FAR-INFRARED SOURCES

We report the results of a systematic search for high-velocity CO emission from a sample of bright (100 μm flux densities > 500 Jy) far-infrared sources from the IRAS Point Source Catalog. This extends our original survey to a complete flux-limited sample. In this paper we present results of CO mapping toward 22 far-infrared sources and find all to be associated with strong CO emission that is peaked close to the far-infrared sources. Based on their infrared colors and positional coincidence with strong CO emission, we believe our sample to be composed entirely of luminous, young stellar objects. New detections of molecular outflows were made toward six of the far-infrared sources; these outflows are relatively energetic, with typical mechanical energies of 1045 ergs. Combining our two surveys and including other published results, we find that roughly 50% of a flux-limited sample of far-infrared sources have energetic molecular outflows. The short lifetime of the outflow phase coupled with the high incidence of outflows is used to set an upper limit of 4 × 105 yr for the lifetime of stars as luminous far-infrared sources. Outflows may make an important contribution to the kinetic energy density within molecular clouds.