Gas flow and the structure of the Galactic bar

The evidence that our galaxy is a barred galaxy will be summarised. The bar's impact on local kinematics and on the flow of the ISM are significant lines of evidence. Hydrodynamical simulations will be used to examine critically the conjecture that gas streamlines approximate closed orbits. It turns out that the sound speed and numerical resolution both play significant roles in structuring the flow. At high resolution the flow becomes unsteady, and there are reasons to believe this unsteadiness is of practical importance. The effect of varying the bar's strength is examined. The data point to a strong and surprisingly slow bar. New models of our Galaxy in which dark matter is fully dynamical confirm a significant uptake of energy and angular momentum by the central portion of the Galaxy's dark halo.