O I 63 micron-determined mass-loss rates in young stellar objects

We present observations of the O I 63 mu m emission toward five young, highly collimated outflow sources: IRAS 16293-2422, VLA 1623, L1448-mm, L1448-IRS 3, and NGC 1333-IRAS 4A. We have partially mapped the O I 63 mu m emission associated with the first three outflows, but have made single-beam observations of the latter two. We discuss how the O I 63 mu m emission can be used to measure mass outflow rates and compare these with the determination of outflow rates from CO observations. We find that the O I-derived mass outflow rates are in good agreement with the CO-derived rates in two of the five sources, but are a factor similar to 2-4 times lower than the CO-derived rates in L1448-mm, L1448-IRS 3, and IRAS 16293-2422. This provides additional support to arguments already made by numerous authors that the CO-derived rates may be overestimates. We discuss the correlation between the spatial distribution of the CO and O I emission and argue that the outflow occurs in multiple events that gradually evacuate the path of the wind through the ambient medium.