CO outflows from young stellar objects

We have mapped the CO J = 1-0 emission from molecular outflows associated with six young stellar systems using the BIMA array. The systems are all relatively nearby, have low-luminosity, and range from Class 0 to Class II sources. The CO outflows in these systems are complicated, showing multipolar structures, multiple cavities, and asymmetric lobes. The complicated appearance of the CO outflows may result from the interactions between one or more outflows and the nonuniform ambient cloud. The CO emission typically arises from shell structures around the outflow axis. For some outflows, there are also clumpy and bowlike structures in CO along the outflow axis within the shell. Comparing the observed outflow features to that of jet- and wind-driven models, we find that the outflow systems show some features that are characteristic of the jet-driven model and others characteristic of the wind-driven model. Simple models of jets or winds cannot reproduce the full range of kinematic features found in observed outflows. The jet-driven model requires jet wandering to produce the observed outflow width and momentum content for most of these outflows, while the wind-driven model needs to have a collimated core with a strong velocity gradient away from the core to produce the highly collimated outflows and the observed curved internal H₂ bow shock structures.