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 $Ω_K$ are allowed to vary, carefully discussing the impact of both $w$ and $Ω_K$ 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 $ε\gtrsim 0.07$, compatible with astrophysical expectations. In contrast, the FRESCO sample requires $ε\gtrsim 0.5$ at $2σ$, with values $ε\lesssim 0.2$ disfavored at $>5σ$. These results do not qualitatively change when we allow $w$ and/or $Ω_K$ to vary, with no evidence for deviations from $w=-1$ or $Ω_K=0$. Our results therefore suggest that the origin of the ``JWST tension'' is unlikely to be cosmological, but lies in the astrophysics of galaxy formation.