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Published July 2009 | Published
Journal Article Open

A dark matter disc in three cosmological simulations of Milky Way mass galaxies

Abstract

Making robust predictions for the phase-space distribution of dark matter at the solar neighbourhood is vital for dark matter direct-detection experiments. To date, almost all such predictions have been based on simulations that model the dark matter alone. Here, we use three cosmological hydrodynamic simulations of bright, disc-dominated galaxies to include the effects of baryonic matter self-consistently for the first time. We find that the addition of baryonic physics drastically alters the dark matter profile in the vicinity of the solar neighbourhood. A stellar/gas disc, already in place at high redshift, causes merging satellites to be dragged preferentially towards the disc plane where they are torn apart by tides. This results in an accreted dark matter disc that contributes ~0.25–1.5 times the non-rotating halo density at the solar position. The dark disc, unlike dark matter streams, is an equilibrium structure that must exist in disc galaxies that form in a hierarchical cosmology. Its low rotation lag with respect to the Earth significantly boosts Weakly Interacting Massive Particle (WIMP) capture in the Earth and Sun, boosts the annual modulation signal and leads to distinct variations in the flux as a function of recoil energy that allow the WIMP mass to be determined.

Additional Information

© 2009 The Authors. Journal compilation © 2009 RAS. Accepted 2009 March 9. Received 2009 March 8; in original form 2008 December 29. We would like to thank the referee for useful comments that improved the paper. JIR would like to acknowledge support from a Forschungskredit grant from the University of Zürich; LM from SNF grant PP0022-110571 and FG from a Theodore Dunham grant, HST GO-1125, NSF ITR grant PHY-0205413 (also supporting TQ), NSF grant AST-0607819 and NASA ATP NNX08AG84G.

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August 20, 2023
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