Hunting for the Dark Matter Wake Induced by the Large Magellanic Cloud

Abstract Satellite galaxies are predicted to generate gravitational density wakes as they orbit within the dark matter (DM) halos of their hosts, causing their orbits to decay over time. The recent infall of the Milky Way’s (MW) most massive satellite galaxy, the Large Magellanic Cloud (LMC), affords us the unique opportunity to study this process in action. In this work, we present high-resolution ( m dm = 4 × 10 4 M ⊙ ) N -body simulations of the MW–LMC interaction over the past 2 Gyr. We quantify the impact of the LMC’s passage on the density and kinematics of the MW’s DM halo and the observability of these structures in the MW’s stellar halo. The LMC is found to generate a pronounced wake, which we decompose in Transient and Collective responses, in both the DM and stellar halos. The wake leads to overdensities and distinct kinematic patterns that should be observable with ongoing and future surveys. Specifically, the Collective response will result in redshifted radial velocities of stars in the north and blueshifts in the south, at distances >45 kpc. The Transient response traces the orbital path of the LMC through the halo (50–200 kpc), resulting in a stellar overdensity with a distinct, tangential kinematic pattern that persists to the present day. The detection of the MW’s halo response will constrain the infall mass of the LMC, its orbital trajectory, and the mass of the MW, and it may inform us about the nature of the DM particle itself.