Joint constraints on thermal relic dark matter from strong gravitational lensing, the Lyman-$\hat{I}\pm$ forest, and Milky Way satellites

Abstract

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 Lyman-$\hat{I}\pm$ forest, and the number of luminous satellites in the Milky Way. We derive an upper limit of $\hat{I}{»}_{\mathrm{hm}}=0.089\mathrm{Mpc}{\mathrm{h}}^{-1}$ 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 $M_{\mathrm{hm}}<3\times 10^7{\mathrm{M}}_{\odot }{\mathrm{h}}^{-1}$, and a lower limit on the particle mass of $m_{\mathrm{th}}>6.048\mathrm{keV}$, both at the 95 per cent confidence level. We find that models with $\hat{I}{»}_{\mathrm{hm}}>0.223\mathrm{Mpc}{\mathrm{h}}^{-1}$ (corresponding to $m_{\mathrm{th}}>2.552\mathrm{keV}$ and $M_{\mathrm{hm}}<4.8\times 10^8{\mathrm{M}}_{\odot }{\mathrm{h}}^{-1}$) are ruled out with respect to the maximum likelihood model by a factor $\le 1/20$. For lepton asymmetries $L_6>10$, we rule out the $7.1\mathrm{keV}$ sterile neutrino dark matter model, which presents a possible explanation to the unidentified $3.55\mathrm{keV}$ 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.

16 pages, 3 Figures, minor updates of the results