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, Fux, 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 galactocentric distance R0 in model units, the orientation angle ϕ, the velocity scale (in km s-1 per model unit), and the solar tangential velocity that best fit the data.