Rotation of the NGC 1333 IRAS 4A2 Protostellar Jet
  The bipolar jet of the NGC 1333 IRAS 4A2 protostar shows a velocity gradient
in the direction perpendicular to the jet axis. This lateral velocity gradient
can be seen throughout the jet imaged in a silicon monoxide line, 2500-8700 AU
from the driving source, and is consistent with the rotation of the accretion
disk. If this gradient is caused by the rotation of the jet around its axis,
the average specific angular momentum is about 1.5 x 10^21 cm^2 s^-1.
Comparison of the kinematics between the jet and the disk suggests that the
jet-launching region on the disk has a radius of about 2 AU, which supports the
disk-wind models. The angular momentum transported away by the jet seems to be
large enough for the protostar to accrete matter from the disk, confirming the
crucial role of jets in the early phase of star formation process.
