Dark Matter Constraints from a Unified Analysis of Strong Gravitational Lenses and Milky Way Satellite Galaxies

Joint analyses of small-scale cosmological structure probes are relatively unexplored and promise to advance measurements of microphysical dark matter properties using heterogeneous data. Here, we present a multidimensional analysis of dark matter substructure using strong gravitational lenses and the Milky Way (MW) satellite galaxy population, accounting for degeneracies in model predictions and using covariances in the constraining power of these individual probes for the first time. We simultaneously infer the projected subhalo number density and the half-mode mass describing the suppression of the subhalo mass function in thermal relic warm dark matter (WDM), Mhm, using the semianalytic model Galacticus to connect the subhalo population inferred from MW satellite observations to the strong lensing host halo mass and redshift regime. Combining MW satellite and strong lensing posteriors in this parameter space yields Mhm < 107.0 M⊙ (WDM particle mass mWDM > 9.7 keV) at 95% confidence and disfavors Mhm = 107.4 M⊙ (mWDM = 7.4 keV) with a 20:1 marginal likelihood ratio, improving limits on mWDM set by the two methods independently by ∼30%. These results are marginalized over the line-of-sight contribution to the strong lensing signal, the mass of the MW host halo, and the efficiency of subhalo disruption due to baryons and are robust to differences in the disruption efficiency between the MW and strong lensing regimes at the ∼10% level. This work paves the way for unified analyses of next-generation small-scale structure measurements covering a wide range of scales and redshifts.