Dark sector constraints from the first galaxies with JWST

by Julian Munoz (Harvard-Smithsonian Center for Astrophysics)

Wednesday 8 Jul 2026, 11:30 → 12:30 Europe/Zurich

4/2-011 - TH common room (CERN)

The James Webb Space Telescope (JWST) has revolutionized our view of the early universe, and I will discuss what cosmology we are learning from its data in two arenas. First, I will show how JWST galaxies provide new tests of dark matter behavior at small scales, constraining models of warm or interacting DM in a regime inaccessible by other probes. In the process, I will briefly discuss how the ultra-massive galaxy candidates recently argued to "break" the LCDM cosmological model cannot have a cosmological origin, and may instead constitute an entirely new astrophysical object. Finally, I will examine how recent JWST observations prefer an earlier reionization, with a higher optical depth, at odds with the CMB and the Lyman-alpha forest, but seemingly preferred by recent DESI dark energy results.