Gas dynamics in the Milky Way: a low pattern speed model
  We present gas flow models for the Milky Way based on high-resolution
grid-based hydrodynamical simulations. The basic galactic potential we use is
from a N-body model constrained by the density of red clump giants in the
Galactic bulge. We augment this potential with a nuclear bulge, two pairs of
spiral arms and additional mass at the bar end to represent the long bar
component. With this combined model we can reproduce many features in the
observed ($l,v$) diagram with a bar pattern speed of $33\; {\rm km}\;{\rm
s}^{-1}\;{\rm kpc}^{-1}$ and a spiral pattern speed of $23\; {\rm km}\;{\rm
s}^{-1}\;{\rm kpc}^{-1}$. The shape and kinematics of the nuclear ring, Bania's
Clump 2, the Connecting arm, the Near and Far 3-kpc arms, the Molecular Ring,
and the spiral arm tangent points in our simulations are comparable to those in
the observations. Our results imply that a low pattern speed model for the bar
in our Milky Way reproduces the observations for a suitable Galactic potential.
Our best model gives a better match to the ($l,v$) diagram than previous high
pattern speed hydrodynamical simulations.
