CO-0.30-0.07: A Peculiar Molecular Clump with an Extremely Broad
  Velocity Width
  The high velocity dispersion compact cloud CO-0.30-0.07 is a peculiar
molecular clump discovered in the central moleculr zone of the Milky Way, which
is characterized by its extremely broad velocity emissions ($\sim 145\ \rm{km
s^{-1}}$) despite the absence of internal energy sources. We present new
interferometric maps of the cloud in multiple molecular lines in frequency
ranges of 265--269 GHz and 276--280 GHz obtained using the Sumbmillimeter
Array, along with the single-dish images previously obtained with the ASTE 10-m
telescope. The data show that the characteristic broad velocity emissions are
predominantly confined in two parallel ridges running through the cloud center.
The central ridges are tightly anti-correlated with each other in both space
and velocity, thereby sharply dividing the entire cloud into two distinct
velocity components (+15 km s$^{-1}$ and +55 km s$^{-1}$). This morphology is
consistent with a model in which the two velocity components collide with a
relative velocity of 40 $\mathrm{km s^{-1}}$ at the interface defined by the
central ridges, although an alternative explanation with a highly inclined
expanding-ring model is yet to be fully invalidated. We have also unexpectedly
detected several compact clumps ($\lesssim 0.1\ $pc in radius) likely formed by
shock compression. The clumps have several features in common with typical
star-forming clouds: high densities ($10^{6.5-7.5}\ \mathrm{cm^{-3}}$), rich
abundances of hot-core-type molecular species, and relatively narrow velocity
widths apparently decoupled from the furious turbulence dominating the cloud.
The cloud CO-0.30-0.07 is possibly at an early phase of star formation activity
triggered by the shock impact.
