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Joint constraints on thermal relic dark matter from strong gravitational lensing, the Ly α forest, and Milky Way satellites

Enzi, Wolfgang and Murgia, Riccardo and Newton, Oliver and Vegetti, Simona and Frenk, Carlos and Viel, Matteo and Cautun, Marius and Fassnacht, Christopher D and Auger, Matt and Despali, Giulia and McKean, John and Koopmans, Léon V E and Lovell, Mark (2021) 'Joint constraints on thermal relic dark matter from strong gravitational lensing, the Ly α forest, and Milky Way satellites.', Monthly Notices of the Royal Astronomical Society, 506 (4). pp. 5848-5862.


We derive joint constraints on the warm dark matter (WDM) half-mode scale by combining the analyses of a selection of astrophysical probes: strong gravitational lensing with extended sources, the Ly α forest, and the number of luminous satellites in the Milky Way. We derive an upper limit of λhm = 0.089 Mpc h−1 at the 95 per cent confidence level, which we show to be stable for a broad range of prior choices. Assuming a Planck cosmology and that WDM particles are thermal relics, this corresponds to an upper limit on the half-mode mass of Mhm < 3 × 107 M⊙ h−1, and a lower limit on the particle mass of mth > 6.048 keV, both at the 95 per cent confidence level. We find that models with λhm > 0.223 Mpc h−1 (corresponding to mth > 2.552 keV and Mhm < 4.8 × 108 M⊙ h−1) are ruled out with respect to the maximum likelihood model by a factor ≤1/20. For lepton asymmetries L6 > 10, we rule out the 7.1 keV sterile neutrino dark matter model, which presents a possible explanation to the unidentified 3.55 keV line in the Milky Way and clusters of galaxies. The inferred 95 percentiles suggest that we further rule out the ETHOS-4 model of self-interacting DM. Our results highlight the importance of extending the current constraints to lower half-mode scales. We address important sources of systematic errors and provide prospects for how the constraints of these probes can be improved upon in the future.

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Publisher statement:This article has been accepted for publication in Monthly notices of the Royal Astronomical Society. ©: 2021 The Author(s). Published by Oxford University Press on behalf of the Royal Astronomical Society. All rights reserved.
Date accepted:29 June 2021
Date deposited:15 November 2021
Date of first online publication:10 July 2021
Date first made open access:15 November 2021

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