Three-Dimensional Distribution of Molecular Gas in the Barred Milky Way

We present a new model of the three-dimensional distribution of molecular gas in the Milky Way Galaxy, based on CO line data. Our analysis is based on a gas-flow simulation of the inner Galaxy using smoothed particle hydrodynamics (SPH) and a realistic barred gravitational potential derived from the observed COBE DIRBE near-IR light distribution. The gas model prescribes the gas orbits much better than a simple circular rotation model and is highly constrained by observations, but it cannot predict local details. In this study, we provide a three-dimensional map of the observed molecular gas distribution using the velocity field from the SPH model. A comparison with studies of the Galactic center region suggests that the main structures are reproduced, but somewhat stretched along the line of sight, probably on account of limited resolution of the underlying SPH simulation. The gas model will be publicly available and may prove useful in a number of applications, among them the analysis of diffuse gamma-ray emission as measured with GLAST.