The Fossil Nuclear Outflow in the Central 30 pc of the Galactic Center
  We report a new 1-pc (30") resolution CS($J=2-1$) line map of the central 30
pc of the Galactic Center (GC), made with the Nobeyama 45m telescope. We
revisit our previous study of the extraplanar feature called polar arc (PA),
which is a molecular cloud located above SgrA* with a velocity gradient
perpendicular to the Galactic plane. We find that the PA can be traced back to
the Galactic disk. This provides clues of the launching point of the PA ,
roughly $6\times10^{6}$ years ago. Implications of the dynamical time scale of
the PA might be related to the Galactic Center Lobe (GCL) at parsec scale. Our
results suggest that in the central 30 pc of the GC, the feedback from past
explosions could alter the orbital path of the molecular gas down to the
central tenth of parsec. In the follow-up work of our new CS($J=2-1$) map, we
also find that near the systemic velocity, the molecular gas shows an
extraplanar hourglass-shaped feature (HG-feature) with a size of $\sim$13 pc.
The latitude-velocity diagrams show that the eastern edge of the HG-feature is
associated with an expanding bubble B1, $\sim$7 pc away from SgrA*. The
dynamical time scale of this bubble is $\sim3\times10^{5}$ years. This bubble
is interacting with the 50 km s$^{-1}$ cloud. Part of the molecular gas from
the 50 km s$^{-1}$ cloud was swept away by the bubble to $b=-0.2deg$. The
western edge of the HG-feature seems to be the molecular gas entrained from the
20 km s$^{-1}$ cloud towards the north of the Galactic disk. Our results
suggest a fossil explosion in the central 30 pc of the GC a few 10$^{5}$ years
ago.
