Bipolar Molecular Outflow from M17
  Kinematics of the molecular clouds in the star forming complex M17 is studied
using the high-resolution CO-line mapping data at resolution ($20" \sim 0.2$
pc) with the Nobeyama 45-m telescope. The northern molecular cloud of M17,
which we call the molecular "lobe", is shown to have an elongated shell
structure around a top-covered cylindrical cavity. The lobe is expanding at
$\sim 5$ \kms in the minor axis direction, and at $ \sim 3/\cos \ i$ km
s$^{-1}$ in the major axis direction, where $i$ is the inclination of the major
axis. The kinetic energy of the expanding motion is on the order of $\sim
3\times 10^{49}$ ergs. We show that the lobe is a backyard structure having the
common origin to the denser molecular "horn" flowing out from NGC 6618 toward
the south, so that the lobe and horn compose a bipolar outflow. Intensity
distributions across the lobe and horn show a double-peak profile typical for a
cylinder around a cavity. Position-velocity diagrams (PVD) across the lobe and
horn exhibit open ring structure with the higher- and/or lower-velocity side(s)
being lacking or faded. This particular PVD behavior can be attributed to
outflow in a conical cylinder with the flow velocity increasing toward the lobe
and horn axes.
