Dark energy, spatial curvature, and star formation efficiency from JWST photometric and spectroscopic high-redshift galaxies

Early observations from the James Webb Space Telescope (JWST) have revealed an overabundance of massive high-redshift galaxies, raising the question of whether this points to new physics beyond $Λ$CDM, or an enhanced formation efficiency of massive stars. We revisit this issue going beyond earlier analyses based on direct comparisons to theoretical bounds at a fixed cosmology, by performing a full Bayesian analysis of the most extreme galaxies in the CEERS imaging and FRESCO spectroscopic samples, jointly constraining cosmological parameters and the baryon-to-star conversion efficiency $ε$. We do so not only within the spatially flat $Λ$CDM model, but also in models where the dark energy equation of state w and/or the spatial curvature parameter ΩK are allowed to vary, carefully discussing the impact of both w and ΩK on the cumulative comoving stellar mass density. Within the flat $Λ$CDM model, once cosmological parameters are marginalized over, the CEERS sample provides a weak $2σ$ lower limit of ε 0.07, compatible with astrophysical expectations. In contrast, the FRESCO sample requires ε 0.5 at $2σ$, with values ε 0.2 disfavored at $>5σ$. These results do not qualitatively change when we allow w and/or ΩK to vary, with no evidence for deviations from $w=-1$ or ΩK=0. Our results therefore suggest that the origin of the ``JWST tension'' is unlikely to be cosmological, but lies in the astrophysics of galaxy formation.