Submillimeter Array Observations of the Molecular Outflow in High-mass Star-forming Region G240.31+0.07

We present Submillimeter Array observations toward the 10 L⊙ starforming region G240.31+0.07, in the J = 2–1 transition of CO and CO and at 1.3 mm continuum, as well as the CO and CO observations from the Caltech Submillimeter Observatory to recover the extended emission filtered out by the interferometer. Maps of the CO and CO emission show a bipolar, wide-angle, quasi-parabolic molecular outflow, roughly coincident with an IR nebula revealed by the Spitzer 3.6 and 4.5 μm emission. The outflow has ∼ 98 M⊙ molecular gas, making it one of the most massive molecular outflows known, and resulting in a very high mass-loss rate of 4.1× 10 M⊙yr −1 over a dynamical timescale of 2.4× 10 yr. The 1.3 mm continuum observations with a 4 × 3 beam reveal a flattened dusty envelope of ∼ 150 M⊙, which is further resolved with a 1.2 ′′ × 1 beam into three dense cores with a total mass of ∼ 40 M⊙. The central mm core, showing evidence of active star formation, approximately coincides with the geometric center of the bipolar outflow thus most likely harbors the powering source of the outflow. Overall our observations provide the best case to date of a well-defined wide-angle molecular outflow in a > 10 L⊙ star-forming region. The outflow is morphologically and kinematically similar to low-mass protostellar outflows but has two to three orders of magnitude greater mass, momentum, and energy, and is apparently driven by an underlying wide-angle wind, hence further supports that high-mass stars up to late-O types, even in a crowded clustering environment, can form as a scaled-up version of low-mass star formation. Subject headings: ISM: individual (G240.31+0.07) — ISM: jets and outflows — stars: formation — stars: early-type Department of Astronomy, Nanjing University, Nanjing, China Harvard-Smithsonian Center for Astrophysics, Cambridge, MA Institute of Astronomy and Department of Physics, National Tsing Hua University, Hsinchu, Taiwan Institute of Astronomy and Astrophysics, Academia Sinica, Taiwan