We present the high angular resolution and high sensitivity images of the “ Circum-Nuclear Disk ( CND ) ” and its surrounding region of Milky Way Galaxy in the CS J = 2 - 1 , SiO v = 0 ~ { } J = 2 - 1 , H ^ { 13 } CO ^ { + } J = 1 - 0 , C ^ { 34 } S J = 2 - 1 , and CH _ { 3 } OH J _ { K _ { a } ,K _ { c } } = 2 _ { 1 , 1 } -1 _ { 1 , 0 } A _ { - - } emission lines using ALMA .
The CND is recognized as a torus-like molecular gas with gaps in these emission lines except for the CH _ { 3 } OH emission line .
The inner and outer radii of the CND are estimated to be R _ { \mathrm { in } } \sim 1.5 and R _ { \mathrm { out } } \sim 2 pc , respectively .
The velocities of the rotation and radial motion are estimated to be V _ { \mathrm { rot } } \sim 115 km s ^ { -1 } and V _ { \mathrm { rad } } \sim 23 km s ^ { -1 } , respectively .
The LTE molecular gas mass is estimated to be M _ { \mathrm { LTE } } \sim 3 \times 10 ^ { 4 } M _ { \odot } .
We also found some anomalous molecular clouds in the surrounding region .
One of the molecular clouds is positionally connected to a part of the CND adjacent to the “ Western Arc ” .
However , the cloud is seen to rotate in the opposite direction to the CND .
The molecular cloud would be falling currently from the outer region to the CND and being disrupted by the tidal shear of Sagittarius A* ( Sgr A* ) because the velocity is not yet assimilated into that of the CND .
Another molecular cloud is continuously connected to the tip of the “ Eastern Arm ( EA ) ” .
The velocity of this cloud is consistent with that of the ionized gas in the EA .
These facts suggest that the molecular cloud is falling from the outer region to the vicinity of Sgr A* , being disrupted by the tidal shear , and ionized by strong UV emission from the Central Cluster because the impact parameter of the cloud is smaller than the first cloud .
These falling clouds would play an important role in transferring material from the outer region to the CND and/or the vicinity of Sgr A* .