Dark Matter Cartography
Building an accurate map of the spatial and velocity distribution of dark matter near the Sun requires understanding how the Milky Way galaxy evolved over time. The Milky Way grows by absorbing smaller galaxies that get caught by its strong gravitational pull. As these small galaxies orbit our own, they are eventually shredded by tidal forces, leaving behind their stars and dark matter. Evidence for such mergers lies in the stars that they leave behind, which can share distinctive clustering patterns in position, velocity, and/or chemical abundance space. We can use the reconstructed properties of these mergers to model the dark matter that was removed from them. Our ongoing work in this area is demonstrating that the local dark matter near the Sun is not in equilibrium, as typically assumed, and instead exhibits distinctive dynamics tied to the disruption of small galaxies. The updated dark matter map that we are building has important ramifications for direct detection experiments, which search for the interactions of these particles in terrestrial targets.