MOMENTUM DISTRIBUTION IN MOLECULAR OUTFLOWS

In this paper we investigate the distribution of momentum in protostellar molecular outflows and make comparisons with recent outflow models. In most flows, momentum peaks are found in the centers of the lobes, with minima toward the protostar and the edges of the flow. The peaks, which are typically offset by similar to 0.1-0.6 pc from the star, are also seen in the distribution of mass, lobe cross-sectional area, and individual channel maps. The shape of the momentum distribution is compared with predictions of several types of models from the literature i,e., outflows driven by wide-angle winds, jet bow shocks, and steady state, turbulent flows, and we find that none of them can account for momentum peaks located in the middle of the lobes. We discuss modifications that would make the models more consistent with the data and argue in favor of a jet/bow shock model in which the jet is variable in velocity and/or angle.