The Extremely High-Velocity Outflow from the Luminous Young Stellar Object G5.89-0.39
Left: Extremely high-velocity molecular outflows of G5.89-0.39 in CO (2-1) imaged with the SMA. Right: The outflowing gas temperature versus the gas velocity deduced from the LVG calculations. An increasing trend of the gas temperature with the outflow velocity can be discerned toward all lobes.
Although molecular outflows have been commonly identified around both low- and high-mass young stellar objects, it is not clear how the bulk of the outflowing gas is accelerated. Exploring the physical conditions of the extremely high-velocity outflowing gas in details will be helpful for clarifying its role in star formation processes. The massive star forming region G5.89-0.39 is associated with energetic CO outflows with velocities up to ~70km s-1 from its systemic velocity, the highest gas velocities that have been detected in molecular outflows. With the SMA observations in CO (2-1) and (3-2), we have for the first time estimated the temperature of the outflowing gas as a function of the velocity. Our results reveal a clear increasing trend of the temperature with the gas velocity. The observational features of the extremely high-velocity gas associated with G5.89-0.39 qualitatively favor the jet-driven bow shock model. (Su et al., 2011, submitted)