CSO CO(2–1) and Spitzer IRAC observations of a bipolar outflow in high-mass star-forming region IRAS 22506+5944

We present Caltech Submillimeter Observatory CO （2-1） and Spitzer IRAC observations toward IRAS 22506＋5944, which is a 104 Lo massive star-forming region. The CO （2-1） maps show an east-west bipolar molecular outflow originating from the 3 mm dust continuum peak. The Spitzer IRAC color-composite image reveals a pair of bow-shaped tips which are prominent in excess 4.5 p.m emission and are located at the leading fronts of the bipolar outflow, providing compelling evidence for the existence of bow-shocks as the driving agents of the molecular outflow. By comparing our CO （2- 1） observations with previously published CO （1-0） data, we find that the CO （2-1）/（1-0） line ratio increases from low （-5 km s- 1） to moderate （- 8-12 km s- 1） velocities, and then decreases at higher velocities. This is qualitatively consistent with the scenario that the molecular outflow is driven by multiple bow-shocks. We also revisit the position-velocity diagram of the CO （1-0） data, and find two spur structures along the outflow axis, which are further evidence for the presence of multiple jet bow- shocks. Finally, power-law fittings to the mass spectrum of the outflow gives power law indexes more consistent with the jet bow-shock model than the wide-angle wind model.

Abstract We present Caltech Submillimeter Observatory CO （2-1） and Spitzer IRAC observations toward IRAS 22506＋5944, which is a 104 Lo massive star-forming region. The CO （2-1） maps show an east-west bipolar molecular outflow originating from the 3 mm dust continuum peak. The Spitzer IRAC color-composite image reveals a pair of bow-shaped tips which are prominent in excess 4.5 p.m emission and are located at the leading fronts of the bipolar outflow, providing compelling evidence for the existence of bow-shocks as the driving agents of the molecular outflow. By comparing our CO （2- 1） observations with previously published CO （1-0） data, we find that the CO （2-1）/（1-0） line ratio increases from low （-5 km s- 1） to moderate （- 8-12 km s- 1） velocities, and then decreases at higher velocities. This is qualitatively consistent with the scenario that the molecular outflow is driven by multiple bow-shocks. We also revisit the position-velocity diagram of the CO （1-0） data, and find two spur structures along the outflow axis, which are further evidence for the presence of multiple jet bow- shocks. Finally, power-law fittings to the mass spectrum of the outflow gives power law indexes more consistent with the jet bow-shock model than the wide-angle wind model.