Abstract

The Galactic bar is one of the main drivers of dynamical evolution in the Milky Way. It redistributes angular momentum, reshapes stellar orbits, and facilitates radial migration—bringing stars, including many exoplanet hosts, from the inner Galaxy into the Solar neighborhood. Understanding the bar’s properties and its interaction with the dark matter halo is therefore essential for reconstructing the formation history of the Milky Way and interpreting the stellar populations we observe locally.

In recent work with Adam Dillamore, we show that distinct chevron-shaped features in the phase-space distribution of halo stars can be explained by resonant interactions with the bar. These features, seen in Gaia data, allow us to infer the bar’s pattern speed and gravitational influence. Because the structure and location of these resonances evolve over time, they also provide clues to the bar’s past growth and its coupling to the dark matter halo. This work opens a new window into bar–halo dynamics and highlights how seemingly distant halo stars can help constrain the internal evolution of the Milky Way.