The Large Magellanic Cloud’s Dynamical Friction Wake in Cold vs. Fuzzy Dark Matter

Despite the successes of dark matter (DM) at explaining a wide range of galaxy properties, DM particles have yet to be directly detected. As such, multiple models for the microphysics of the DM particle remain viable, such as cold DM (CDM) and fuzzy DM (FDM). A major goal of theoretical astrophysics is to make predictions to distinguish between these scenarios. In galactic evolution, DM serves as the primary driver of galaxy mergers by providing a medium for dynamical friction. The Milky Way’s (MW) largest satellite, the Large Magellanic Cloud, (LMC) has been predicted to generate a DM density wake during its ongoing first infall to the MW (Garavito-Camargo+2019, ApJ, 884, 51). This scenario provides a novel opportunity to use the LMC’s wake to probe the nature of the DM particle. We present a suite of high-resolution, windtunnel-style simulations of the LMC’s wake that compare the structure, kinematics, and stellar tracer response to the DM wake in CDM vs. FDM. We show that an FDM wake is more granular in structure and is dynamically colder than a CDM wake. Crucially, we find that the kinematic response of stars in CDM is stronger than in FDM, presenting a plausible method of observationally distinguishing between these two competing DM models. Additionally, the self-gravity of the DM wake plays a key role in keeping it coherent over large distances and affects the distribution and kinematics of stellar tracers. The length of the stellar wake can thus be used as independent evidence for the existence of DM. We present specific observing strategies to test our predictions with spectroscopic surveys such as DESI.