Dark Secrets of Baryons: Illuminating Dark Matter–Baryon Interactions with JWST

The James Webb Space Telescope (JWST) has discovered bright galaxies at high redshifts (z≈10-14) and various galaxy candidates extending to even higher redshifts (z≈15-30). Many astrophysical and beyond the Standard Model physics scenarios have been proposed to explain these observations. We investigate, for the first time, the implications of dark matter (DM) scattering with baryons (protons and electrons) in light of the JWST UV luminosity function (UVLF) observations. These interactions suppress structure formation on galactic scales, which may have an observable effect on the UVLF measurements at high redshifts. Using a recent galaxy formation model designed to explain high-redshift observations, we obtain strong upper limits on DM-baryon scattering cross sections and explore new regions of the parameter space. For DM-proton scattering with cross section ∝v^{-2} velocity dependence, we obtain the strongest limit for DM masses of ∼1-500 MeV. For other cases that we study (DM-proton scattering cross section ∝v^{0},v^{-4} and DM-electron scattering cross section ∝v^{0},v^{-2},v^{-4}), our limits are competitive with those obtained from other cosmological observables. Our Letter highlights the potential of JWST observations as a novel and powerful probe of nongravitational interactions of DM.