Using spectral-line observations of HNCO , N _ { 2 } H ^ { + } , and HNC , we investigate the kinematics of dense gas in the central \sim 250 pc of the Galaxy .
We present scouse ( S emi-automated multi- CO mponent U niversal S pectral-line fitting E ngine ) , a line-fitting algorithm designed to analyse large volumes of spectral-line data efficiently and systematically .
Unlike techniques which do not account for complex line profiles , scouse accurately describes the \ { l, b, v _ { LSR } \ } distribution of Central Molecular Zone ( CMZ ) gas , which is asymmetric about Sgr A* in both position and velocity .
Velocity dispersions range from 2.6 { km s ^ { -1 } } < \sigma < 53.1 { km s ^ { -1 } } .
A median dispersion of 9.8 km s ^ { -1 } , translates to a Mach number , \mathcal { M } _ { 3 D } \geq 28 .
The gas is distributed throughout several ‘ ‘ streams ’ ’ , with projected lengths \sim 100 - 250 pc .
We link the streams to individual clouds and sub-regions , including Sgr C , the 20 and 50 km s ^ { -1 } clouds , the dust ridge , and Sgr B2 .
Shell-like emission features can be explained by the projection of independent molecular clouds in Sgr C and the newly identified conical profile of Sgr B2 in \ { l, b, v _ { LSR } \ } space .
These features have previously invoked supernova-driven shells and cloud-cloud collisions as explanations .
We instead caution against structure identification in velocity-integrated emission maps .
Three geometries describing the 3-D structure of the CMZ are investigated : i ) two spiral arms ; ii ) a closed elliptical orbit ; iii ) an open stream .
While two spiral arms and an open stream qualitatively reproduce the gas distribution , the most recent parameterisation of the closed elliptical orbit does not .
Finally , we discuss how proper motion measurements of masers can distinguish between these geometries , and suggest that this effort should be focused on the 20 km s ^ { -1 } and 50 km s ^ { -1 } clouds and Sgr C .