Modeling the large-scale gas features of the Milky Way

Studies of atomic and molecular gas in our Galaxy have revealed strong non-circular motions, which are now understood to be caused mainly by the Galactic bar and the spiral arms. Due to the unknown distances to individual gas clouds, these data are commonly presented in the (l,v) diagram, which shows the distribution of gas emission-line intensity as a function of Galactic longitude and the line-of-sight velocity. I will briefly review previous attempts to interpret the observed (l,v) diagram, and then present our hydrodynamical simulations based on the latest VVV survey. We suggest that the nuclear bulge, the primary spiral arms, the bulge bar, and the long bar are essential for certain features in the (l,v) diagram. Our results imply that a relatively slower Galactic bar could also reproduce the observations for a suitable Galactic potential, and our best model gives a better match to the (l,v) diagram than previous high pattern speed models. By applying the tangent point method to our simulations, we show that the inner Galactic rotation curve could be strongly overestimated and needs to be corrected when encountering certain gas structures.