A dark disc in the Milky Way

Predicting the flux of dark matter particles through the Earth is vital for current and future direct dark matter detection experiments. To date, such predictions have been based on simulations that model the dark matter alone. Here we make the first attempt to include the influence of the baryonic matter. We show that the presence of a stellar/gas disc at high redshift (z ∼ 1) causes merging satellites to be preferentially dragged towards the disc plane. This results in an accreted stellar disc, and a dark matter disc that contributes PDDISO = 0.25-1 ρ_HALO at the solar position. Although not likely to be dynamically interesting, the dark disc has important implications for the direct detection of dark matter because of its low velocity with respect to the Earth.