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Abstract The SMC orbits within the LMC’s dark matter (DM) halo in a ∼1:10 mass-ratio encounter. The LMC–Milky Way (MW) interaction is also ∼1:10, and is expected to perturb the MW’s DM distribution. However, no framework exists to quantify the severity of these perturbations over multiple pericenters and longer periods of time, such as the LMC–SMC interaction history. We construct basis function expansions of a high-resolutionN-body simulation of the Clouds interacting in isolation and analyze their DM distributions at an epoch approximating the time of their infall to the MW. Our goal is to quantify how the Clouds distort each other’s DM distributionswithoutthe MW. The LMC halo’s response to the SMC includes a ∼20 kpc long dynamical friction wake and the displacement of the LMC’s density center during each SMC pericenter, which produces two overdensities in the LMC halo (at ∼60 and ∼100 kpc) at MW infall. The SMC’s tidal radius at infall is just ∼4 kpc, at which point the SMC has lost two-thirds of its initial DM mass to the LMC. The distortions to the Clouds’ halos produce a highly asymmetric acceleration field. Accurate orbit integration in the LMC–SMC system must account for the time-dependent shapes of both halos. The SMC-induced perturbations in the LMC DM halo resemble the MW–LMC system, and persist over multiple SMC pericenters. We conclude that 1:10 satellite–host encounters induce characteristic deformations in both DM halos across host-mass scales, with implications for merger rates and tests of DM models.
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The impact of the Large Magellanic Cloud on dark matter direct detection signals
Abstract We study the effect of the Large Magellanic Cloud (LMC) on the dark matter (DM) distribution in the Solar neighborhood, utilizing the Auriga magneto-hydrodynamical simulations of Milky Way (MW) analogues that have an LMC-like system. We extract the local DM velocity distribution at different times during the orbit of the LMC around the MW in the simulations. As found in previous idealized simulations of the MW-LMC system, we find that the DM particles in the Solar neighborhood originating from the LMC analogue dominate the high speed tail of the local DM speed distribution. Furthermore, the native DM particles of the MW in the Solar region are boosted to higher speeds as a result of a response to the LMC's motion.We simulate the signals expected in near future xenon, germanium, and silicon direct detection experiments, considering DM interactions with target nuclei or electrons. We find that the presence of the LMC causes a considerable shift in the expected direct detection exclusion limits towards smaller cross sections and DM masses, with the effect being more prominent for low mass DM. Hence, our study shows, for the first time, that the LMC's influence on the local DM distribution is significant even in fully cosmological MW analogues.
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- Award ID(s):
- 1941096
- PAR ID:
- 10515626
- Publisher / Repository:
- JCAP
- Date Published:
- Journal Name:
- Journal of Cosmology and Astroparticle Physics
- Volume:
- 2023
- Issue:
- 10
- ISSN:
- 1475-7516
- Page Range / eLocation ID:
- 070
- Format(s):
- Medium: X
- Sponsoring Org:
- National Science Foundation
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- Free Publicly Accessible Full Text
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Accepted Manuscript
- Journal Article:
- https://doi.org/10.1088/1475-7516/2023/10/070
