Gas density and velocity fields for a model of the Milky Way

This page makes available model gas density and velocity fields for the inner Milky Way, from B.J. Weiner and J.A. Sellwood, 1999, ApJ, 524, 112. This is a pretty old model but useful because it has a well-sampled density and velocity field over the inner Galaxy. These can be compared to distances and velocities for objects - for example, since non-circular motions in the inner Milky Way are large due to the bar, distances derived from the traditional tangent-point method and a circular rotation curve are suspect.

The model was derived by running gas-dynamical simulations in a variety of potentials, comparing them to the outer envelope of the H I longitude-velocity diagram, and iteratively adjusting the potential parameters and bar viewing angle to improve the comparison. (The parameter space was too large to brute-force search it.) See the paper for more details. The tar file of density and velocity fields contains a Readme file and FITS images of the gas surface density, velocity in x direction, and velocity in y direction. The grid size is 50 pc/pixel, and the bar is at a 45 degree angle to the grid. The best fit GC-Sun line is at a 34 degree angle to the bar, so 79 degrees from the x-axis of the model grid, and the GC to Sun distance is taken to be 8.5 kpc. These models are only strongly constrained inside the bar radius and the model potential didn't include spiral arms, so the density and velocity fields are most useful inside about 4 kpc radius.

For questions about the data or paper please contact Ben Weiner, bjw -at-

Benjamin Weiner

MIPS Group

Steward Observatory