Maser Emission toward the Infrared Dark Cloud G359.94+0.17 Seen in
  Silhouette against the Galactic Center
  The infrared dark cloud G359.94+0.17 is a conspicuous, opaque cloud, which is
seen in silhouette against the Galactic center. We found unexpectedly strong
(~50 Jy) maser emission of CH3OH at 44 GHz with additional weak 22 GHz H2O
maser and 43 GHz SiO thermal emissions toward this cloud. Detections of these
molecular lines indicate that strong star forming activities are proceeding in
this cloud, which were not reported previously despite of numerous works toward
the Galactic center. The line profiles of the NH3 inversion lines at 23 GHz
indicate that G359.94+0.17 is composed of mainly two clouds with V(lsr)= 0, and
15 km/s overlapped on the line of sight. The maser emission is associated with
the 15 km/s cloud, suggesting that it is located at the Norma spiral arm.
