Massive Molecular Outflows at High Spatial Resolution

We present high spatial resolution Plateau de Bure Interferometer CO (2-1) and SiO (2-1) observations of one intermediate-mass and one high-mass star-forming region. The intermediate-mass region IRAS 20293+3952 exhibits four molecular outflows, one being as collimated as the highly collimated jetlike outflows observed in low-mass star formation sources. Furthermore, comparing the data with additional infrared H 2 and centimeter observations, we see indications that the nearby ultracompact H II region triggers a shock wave interacting with the outflow. The high-mass region IRAS 19217+1651 exhibits a bipolar outflow as well, and the region is dominated by the central driving source. Adding two more sources from the literature, we compare position-velocity diagrams of the intermediate-to-high-mass sources with previous studies in the low-mass regime. We find similar kinematic signatures; some sources can be explained by jet-driven outflows, whereas others are better constrained by wind-driven models. The data also allow us to estimate accretion rates varying from a few times 10 -5 M ☉ yr -1 for the intermediate-mass sources to a few times 10 -4 M ☉ yr -1 for the high-mass source, consistent with models explaining star formation of all masses via accretion processes.