We present high resolution H41 \alpha hydrogen recombination line observations of the 1.2 \arcmin ( 3 pc ) region surrounding Sagittarius A ^ { \star } ( Sgr A ^ { \star } ) at 92 GHz using the Millimeter Array at the Owens Valley Radio Observatory ( OVRO ) with an angular resolution of 7 \arcsec \times 3 \arcsec and velocity resolution of 13 km s ^ { -1 } .
New observations of H31 \alpha , H35 \alpha , H41 \alpha and H44 \alpha lines were obtained using the NRAO 12-m telescope , and their relative line strengths are interpreted in terms of various possible emission mechanisms .
These NRAO 12-m measurements are the most extensive recombination line survey of this region to date .
These OVRO data also represent the highest angular resolution and the highest sensitivity observations of Sgr A West in hydrogen recombination line and continuum emission at the millimeter ( mm ) wavelengths .
Observations of HCO ^ { + } ( J = 1 \rightarrow 0 ) transition at 89 GHz are obtained simultaneously with a 40 % improved angular resolution and 4-15 times improved sensitivity over the previously published results , and the distribution and kinematics of the dense molecular gas in the circumnuclear disk ( CND ) are mapped and compared with those of the ionized gas .
The line brightness ratios of the hydrogen recombination lines are consistent with purely spontaneous emission from T _ { e } \sim 7000 K gas with n _ { e } \sim 2 \times 10 ^ { 4 } cm ^ { -3 } near LTE condition .
A virial analysis suggests that the most prominent molecular gas clumps in the CND have mean densities of order 10 ^ { 7 } cm ^ { -3 } , sufficient to withstand the tidal shear in the Galactic Center region .
Therefore , these clumps may survive over several dynamical times , and the CND may be a dynamically stable structure .
We estimate a total gas mass of about 3 \times 10 ^ { 5 } M _ { \odot } for the CND .
Our combined analysis of the new high resolution H41 \alpha and HCO ^ { + } images and our kinematic model demonstrates a widely spread physical and dynamical link between the molecular gas in the CND and the ionized gas , including along the eastern rim of the CND where a gap was previously suggested .