Limits on the Light Dark Matter-Proton Cross Section from Cosmic Large-Scale Structure.

We set the strongest limits to date on the velocity-independent dark matter (DM)-proton cross section σ for DM masses m=10 keV to 100 GeV, using large-scale structure traced by the Lyman-alpha forest: e.g., a 95% lower limit σ<6×10^{-30} cm^{2}, for m=100 keV. Our results complement direct detection, which has limited sensitivity to sub-GeV DM. We use an emulator of cosmological simulations, combined with data from the smallest cosmological scales used to date, to model and search for the imprint of primordial DM-proton collisions. Cosmological bounds are improved by up to a factor of 25.

Strong Bound on Canonical Ultralight Axion Dark Matter from the Lyman-Alpha Forest.

We present a new bound on the ultralight axion (ULA) dark matter mass m_{a}, using the Lyman-alpha forest to look for suppressed cosmic structure growth: a 95% lower limit m_{a}>2×10^{-20} eV. This strongly disfavors (>99.7% credibility) the canonical ULA with 10^{-22} eV