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

Abstract

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 $\Lambda$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 $\Lambda$CDM model, but also in models where the dark energy equation of state $w$ and/or the spatial curvature parameter ${\Omega }_K$ are allowed to vary, carefully discussing the impact of both $w$ and ${\Omega }_K$ on the cumulative comoving stellar mass density. Within the flat $\Lambda$CDM model, once cosmological parameters are marginalized over, the CEERS sample provides a weak $2\sigma$ lower limit of $ϵ\gtrsim 0.07$, compatible with astrophysical expectations. In contrast, the FRESCO sample requires $ϵ\gtrsim 0.5$ at $2\sigma$, with values $ϵ\lesssim 0.2$ disfavored at $>5\sigma$. These results do not qualitatively change when we allow $w$ and/or ${\Omega }_K$ to vary, with no evidence for deviations from $w=-1$ or ${\Omega }_K=0$. Our results therefore suggest that the origin of the ``JWST tension'' is unlikely to be cosmological, but lies in the astrophysics of galaxy formation.

Comments: 36 pages, 8 sub-figures arranged into 6 figures, key figure with clear visual summary of results is Fig. 6. Version accepted for publication in JHEAp