A Schwarzschild model of the Galactic bar with initial density from N-body simulations

TL;DR

This paper constructs a detailed Schwarzschild model of the Galactic bar using N-body simulation data, identifying optimal pattern speed and orientation, and assessing its stability and observational consistency.

Contribution

It introduces a Schwarzschild modeling approach for the Galactic bar based on N-body simulation initial conditions, providing new constraints on bar parameters and stability.

Findings

Best-fit pattern speed is 40 km/s/kpc.

Bar model remains stable for over 1.5 Gyrs.

Predicted proper motions are slightly larger than observed.

Abstract

Using the potential from N-body simulations, we construct the Galactic bar models with the Schwarzschild method. By varying the pattern speed and the position angle of the bar, we find that the best-fit bar model has pattern speed $\Omega_{\rm p}=40\ \rm{km\ s^{-1}\ kpc^{-1}}$, and bar angle $\theta_{\rm bar}=45^{\circ}$. $N$-body simulations show that the best-fit model is stable for more than 1.5 Gyrs. Combined with the results in Wang et al. (2012), we find that the bar angle and/or the pattern speed are not well constrained by BRAVA data in our Schwarzschild models. The proper motions predicted from our model are slightly larger than those observed in four fields. In the future, more kinematic data from the ground and space-based observations will enable us to refine our model of the Milky Way bar.