Clustering constraints on super-early galaxy formation scenarios

Abstract

The unexpectedly high abundance of bright, blue, super-early galaxies ($z\gtrsim 10$) has challenged most pre-JWST models of early galaxy formation and motivated a wide range of proposed explanations. We systematically investigate whether galaxy clustering can discriminate among representative scenarios that reproduce the observed UV luminosity function. Using the Shin-Uchuu dark-matter-only simulation, we populate $z\approx 11$ halos with galaxies according to solutions based on i) attenuation-free, ii) feedback-free bursts, iii) bursty star formation, and iv) primordial black hole models. For each model, we compute the two-point correlation function and predict the galaxy bias for flux-limited samples at different thresholds in the $-20<{\mathrm{M}}_{\mathrm{UV}}<-16$ magnitude range. We find that all models predict similar bias values ($b\approx 7$) for faint galaxies (${\mathrm{M}}_{\mathrm{UV}}\approx -16$), but diverge at ${\mathrm{M}}_{\mathrm{UV}}\lesssim -18$, as the underlying halo-mass to ${\mathrm{M}}_{\mathrm{UV}}$ relations differ significantly. In particular, the primordial black hole scenario predicts an almost luminosity-independent bias, whereas the other models generally predict increasing bias with luminosity, reaching $b\approx 14$ for ${\mathrm{M}}_{\mathrm{UV}}\approx -19$. Current observational estimates of the bias cannot yet rule out any of the models at a significant statistical confidence. More precise measurements from future JWST programs, together with improved theoretical predictions, will be required to break the present degeneracies. Ideally, constraints from a complete sample of galaxies with ${\mathrm{M}}_{\mathrm{UV}}<-18$ would probe the knee of the $b({\mathrm{M}}_{\mathrm{UV}})$ function, taking advantage of the difference in model predictions and strengthening our analysis. Although requiring further refinement, galaxy clustering is confirmed to be a promising probe of the physical origin of the JWST high-redshift luminosity function.

9 pages, 4 figures, 1 table, submitted to A&A. Comments welcome