Gas Dynamics in the Galaxy: Total Mass Distribution and the Bar Pattern Speed

Gas morphology and kinematics in the Milky Way contain key information for understanding formation evolution of our Galaxy. We present a high resolution hydrodynamical simulation based on realistic barred potential constrained by recent observations. Our model can reproduce most features observed longitude-velocity diagram, including Central Molecular Zone, Near Far 3-kpc arms, Ring, spiral arm tangents. It also explain non-circular motions masers obtained BeSSeL2 survey. The central gas are consistent with mass $6.9\times10^8\; {\rm M}_{\odot}$ Nuclear Stellar Disk. predicts an elliptical gaseous ring surrounding bar, which is composed Norma arm, bar-spiral interfaces. This similar to those "inner" rings some analogs boxy/peanut-shaped bulge. near solar neighbourhood governed Local induced four major stellar arms. bar pattern speed $37.5-40\; km}\;{\rm s}^{-1}\;{\rm kpc}^{-1}$, corresponding corotation radius $R_{\rm CR}=6.0-6.4\;{\rm kpc}$. rotation curve rises gently within $\sim5\;{\rm kpc}$, significantly less steep than predicted modern zoom-in cosmological simulations such as Auriga.