Very high velocity emission from molecular outflows

Very low noise spectra of emission from the J = 1 - 0 transition of CO in nine molecular outflows are presented. All the spectra exhibit emission at higher velocities than has been found from more noisy spectra of these outflows taken in the past. In the cases of AFGL 490, NGC 2071, L723 and S140 the highest velocity emission observed may comprise a component in the line wings distinct from the lower velocity wing emission which arises from the swept-up outflowing molecular gas. It is possible that the very high velocity emission observed may arise from gas entrained in the driving winds of these outflows. The outflows which exhibit the most striking high-velocity emission are probably the youngest in our sample. This is consistent with a picture in which molecular outflows are driven by winds which do not blow for their entire lifetimes. In addition, the gas moving at very high velocities in some outflows may carry a considerable amount of mechanical energy, perhaps as much as has been attributed to lower velocity gas in these outflows from analysis of more noisy spectra taken in the past. 19 refs