Dynamics of the Galactic Bulge Using Planetary Nebulae

Evidence for a bar at the center of the Milky Way triggered a renewed enthusiasm for dynamical modeling of the Galactic bar-bulge. Our goal is to compare the kinematics of a sample of tracers, planetary nebulae, widely distributed over the bulge with the corresponding kinematics for a range of models of the inner Galaxy. Three of these models are N-body barred systems arising from the instabilities of a stellar disk (Sellwood, Fur, and Kalnajs), and one is a Schwarzschild system constructed to represent the three-dimensional distribution of the COBE/DIRBE near-IR light and then evolved as an N-body system for a few dynamical times (Zhao). For the comparison of our data with the models, we use a new technique developed by Saha. The procedure finds the parameters of each model, i.e., the solar galacto-centric distance R-0 in model units, the orientation angle phi, the velocity scale (in km s(-1) per model unit), and the solar tangential velocity that best fit the data.