Large Magellanic Cloud May Significantly Alter Dark Matter Detection Signatures
A new study using cosmological simulations finds that the gravitational influence of the Large Magellanic Cloud (LMC) creates strong asymmetries in the directional dark matter recoil signals detectable on Earth. The LMC, as the Milky Way's most massive satellite galaxy, perturbs the local dark matter distribution in ways that deviate from the Standard Halo Model by up to ~80% near signal peaks. These distortions could actually improve detection sensitivity, reducing the number of events needed to confirm a directional dark matter signal by nearly a factor of five in next-generation experiments.
Researchers have used the Auriga suite of cosmological simulations — modeling a Milky Way analogue hosting a Large Magellanic Cloud (LMC) analogue — to investigate how the LMC's gravitational influence reshapes the local dark matter (DM) distribution and its observational signatures. They find that the LMC induces pronounced anisotropies in directional recoil maps, driven chiefly by a non-zero mean azimuthal velocity component in the local DM velocity field. The characteristic ring-like recoil pattern predicted by the Standard Halo Model (SHM) for heavy DM at low recoil energies is strongly distorted into an asymmetric pattern concentrated at preferred azimuthal angles, with deviations from the SHM reaching up to ~80% near the signal maximum. Crucially, these distortions are not merely a complication: they enhance the statistical power of directional detection experiments, reducing the number of events required to reject isotropy by nearly a factor of five for a 100 GeV DM particle in a CYGNUS-like detector, with even larger gains for heavier DM candidates. The results underscore that accurate modeling of the LMC's gravitational perturbation is essential both for correctly interpreting future directional DM search results and for optimizing experimental strategies.
What's missing
The study relies on a single suite of simulations (Auriga) and a specific MW-LMC analogue system; it is unclear how sensitive the results are to the choice of simulation or the degree of LMC-MW mass ratio match. The paper does not quantify uncertainties arising from the unknown LMC infall history or the local DM density normalization.
What different sources said
- arXiv astro-phCenter
Directional dark matter signatures of the Large Magellanic Cloud
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