Discovery of Extremely High Velocity "Molecular Bullets" in the HH 80-81
  High-Mass Star-Forming Region
  We present Submillimter Array 1.3 mm waveband continuum and molecular line
observations of the HH 80-81 high-mass star-forming region. The dust continuum
emission reveals two dominant peaks MM1 and MM2, and line emission from
high-density tracers suggests the presence of another core MC. Molecular line
emission from MM1, which harbors the exciting source of the HH 80-81 radio jet,
yields a hot molecular core at a gas temperature of 110 K. The two younger
cores MM2 and MC both appear to power collimated CO outflows. In particular,
the outflow arising from MM2 exhibits a jet-like morphology and a broad
velocity range of 190 km/s. The outflow contains compact and fast moving
molecular clumps, known as "molecular bullets" first discovered in low-mass
class 0 protostellar outflows. These "bullets" cannot be locally entrained or
swept up from the ambient gas, but are more likely ejected from the close
vicinity of the central protostar. The discovery of this remarkable outflow
manifests an episodic, disk-mediated accretion for massive star formation.
