The Waltz of the Milky Way and the LMC

Denis Erkal (University of Surrey)

April 24, 2023

–

Abstract: In this talk I will present multiple lines of evidence which all suggest that the LMC is a massive companion of our Galaxy, with a mass roughly one-sixth that of the Milky Way. This large of an LMC has many implications: our Galaxy can no longer be thought of as in isolation and many of the structures in our Galaxy should be perturbed. First, the LMC should induce a substantial (~30-40 km/s) reflex motion in the Milky Way. I will present evidence of this reflex motion in both the Milky Way’s stellar halo and its population of satellites. Along similar lines, the passage of LMC should induce a wake in the stellar halo of Milky Way along its past orbit and I will present evidence of this. Finally, I will show how the LMC has affected stellar streams in the Milky Way and how we can use these streams to measure the mass of the LMC. I will focus on the OC stream whose passage with the LMC roughly 300 Myr ago allows us to measure the past orbit of the LMC and how much dynamical friction it has experienced during this time. I will end with a discussion of how streams can be used to measure the deforming dark matter haloes of the Milky Way and LMC and how we can use these to better understand the nature of dark matter.