Kinematics of Ultra-High-Velocity Gas in the Expanding Molecular Shell
  adjacent to the W44 Supernova Remnant
  We mapped the ultra-high-velocity feature (the "Bullet") detected in the
expanding molecular shell associated with the W44 supernova remnant using the
Nobeyama Radio Observatory 45-m telescope and the ASTE 10-m telescope. The
Bullet clearly appears in the CO ${\it J}$=1-0, CO ${\it J}$=3-2, CO ${\it
J}$=4-3, and HCO$^+$ ${\it J}$=1-0 maps with a compact appearance ($0.5\times
0.8$ pc$^2$) and an extremely broad velocity width ($\Delta V\!\simeq\!100 \
\rm km \, s ^{-1}$). The line intensities indicate that the Bullet has a higher
density and temperature than those in the expanding molecular shell. The
kinetic energy of the Bullet amounts to $10^{48.0} \ {\rm erg}$ which is
approximately 1.5 orders of magnitude greater than the kinetic energy shared to
the small solid angle of it. Two possible formation scenarios with an inactive
isolated black hole (BH) are presented.
