Constraints on warm dark matter from UV luminosity functions of high-<i>z</i> galaxies with Bayesian model comparison

The number density of small dark matter (DM) halos hosting faint high-redshift galaxies is sensitive to the DM free-streaming properties. However, constraining these properties complicated by degeneracies with uncertain baryonic physics governing star formation. In this work, we use a flexible astrophysical model and Bayesian inference framework analyse ultra-violet (UV) luminosity functions (LFs) at z=6-8. We vary complexity galaxy (single vs double power law for stellar -- halo mass relation) as well spectrum (cold thermal relic warm DM), comparing their evidences. Adopting conservatively wide prior range WDM particle mass, show that UV LFs z=6-8 only weakly favour CDM over WDM. find masses $\lesssim$2 keV are rejected 95% credible level in all models have WDM-like cutoff. This bound should increase ~2.5 James Webb Space Telescope (JWST).