A New Model for the Milky Way Bar

Abstract

We use Schwarzschild's orbit-superposition technique to construct self-consistent models of the Galactic bar. Using ${\chi }^2$ minimisation, we find that the best-fit Galactic bar model has a pattern speed ${\Omega }_{\mathrm{p}}=60\mathrm{km}{\mathrm{s}}^{-1}\mathrm{kp}{\mathrm{c}}^{-1}$, disk mass ${\mathrm{M}}_{\mathrm{d}}=1.0\times 10^{11}{\mathrm{M}}_{\odot }$ and bar angle ${\theta }_{\mathrm{bar}}=20^{\circ }$ for an adopted bar mass ${\mathrm{M}}_{\mathrm{bar}}=2\times 10^{10}{\mathrm{M}}_{\odot }$. The model can reproduce not only the three-dimensional and projected density distributions but also velocity and velocity dispersion data from the BRAVA survey. We also predict the proper motions in the range $l=[-12^{\circ },12^{\circ }]$, $b=[-10^{\circ },10^{\circ }]$, which appear to be higher than observations in the longitudinal direction. The model is stable within a timescale of 0.5 Gyr, but appears to deviate from steady-state on longer timescales. Our model can be further tested by future observations such as those from GAIA.

16 pages, 21 figures, 5 tables. Accepted for publication in MNRAS

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