GALACTIC STRUCTURE FROM THE SPACELAB INFRARED TELESCOPE .3. A DYNAMIC-MODEL FOR THE MILKY-WAY BULGE

The Milky Way bulge is modeled as an oblate isotropic rotator with constant M/L ratio. A model with M/L2.2-mu-m) = 1 successfully reproduces a variety of stellar velocity dispersion measurements for 2 < R < 1200 pc. An observed increase in the stellar velocity dispersion inside 2 pc requires either that there be an additional central mass of order 3 x 10(6) M. or that the stellar motions become anisotropic there. The model has insufficient mass to reproduce the observed peak in the H I and CO rotation curve of 250 km s-1 at 300 pc; it is argued that the peak arises from noncircular gas motions and does not reflect the true mass of the bulge.