Velocity dipoles in the halos of FIRE simulated galaxies

One major source of disequilibrium in the Milky Way is its most massive satellite, the LMC. Kinematics of distant halo tracers show a velocity dipole in the Milky Way halo, which has been interpreted using N-body simulations as the LMC inducing a reflex motion in the Milky Way disk. In this talk, I discuss applying this framework to more realistic halos comprised of substructure from the FIRE-2 zoom-in cosmological simulations. Velocity dipoles are resolved in Milky Way-mass hosts experiencing an LMC-like interaction and evolve in a manner consistent with a two-body interaction between the stellar disk and the LMC analog. However, satellite galaxies and stellar streams can create velocity dipoles in systems that aren’t experiencing a major satellite accretion, suggesting that care must be taken to remove substructure in the Milky Way observations.