M0.20-0.033: An Expanding Molecular Shell in the Galactic Center Radio
  Arc
  We present high-frequency Karl G. Jansky Very Large Array (VLA) continuum and
spectral line (NH3, H64${\alpha}$, and H63${\alpha}$) observations of the
Galactic Center Radio Arc region, covering the Sickle H II region, the
Quintuplet cluster, and molecular clouds M0.20-0.033 and M0.10-0.08. These
observations show that the two velocity components of M0.20-0.033 (~25 & 80
km/s), previously thought to be separate clouds along the same line-of-sight,
are physically connected in position-velocity space via a third southern
component around 50 km/s. Further position-velocity analysis of the surrounding
region, using lower-resolution survey observations taken with the Mopra and
ATCA telescopes, indicates that both molecular components in M0.20-0.033 are
physically connected to the M0.10-0.08 molecular cloud, which is suggested to
be located on stream 1 in the Kruijssen et al. (2015) orbital model. The
morphology and kinematics of the molecular gas in M0.20-0.033 indicate that the
two velocity components in M0.20-0.033 constitute an expanding shell. Our
observations suggest that the M0.20-0.033 expanding shell has an expansion
velocity of 40 km/s, with a systemic velocity of 53 km/s, comparable to
velocities detected in M0.10-0.08. The origin of the expanding shell is located
near the Quintuplet cluster, suggesting that the energy and momentum output
from this massive stellar cluster may have contributed to the expansion.
