APEX CO (9-8) Mapping of an Extremely High-Velocity and Jet-like Outflow
  in a High-Mass Star-Forming Region
  Atacama Pathfinder Experiment (APEX) mapping observations in CO (9-8) and
(4-3) toward a high-mass star-forming region, NGC 6334 I, are presented. The CO
(9-8) map has a 6.4 arcsec resolution, revealing a ~0.5 pc, jet-like, and
bipolar outflow. This is the first map of a molecular outflow in a THz line.
The CO (9-8) and (4-3) lines arising from the outflow lobes both show extremely
high-velocity line wings, and their ratios indicate a gas temperature greater
than 100 K and a density higher than 10^4 cm^{-3}. The spatial-velocity
structure of the CO (9-8) data is typical of a bow-shock-driven flow, which is
consistent with the association between the bipolar outflow and the infrared
bow-shaped tips. In short, the observations unveil a highly-excited and
collimated component in a bipolar outflow that is powered by a high-mass
protostar, and provide insights into the driving mechanism of the outflow.
Meanwhile, the observations demonstrate that high-quality mapping observations
can be performed with the new THz receiver on APEX.
