The Cosmic Timeline Implied by the JWST Reionization Crisis

Abstract

JWST's discovery of well-formed galaxies and supermassive black holes only a few hundred Myr after the big bang, and the identification of polycyclic aromatic hydrocarbons (PAHs) at $z=6.71$, seriously challenge the timeline predicted by $\Lambda$CDM. Now, a recent analysis of reionization after JWST by Munoz et al. (2024) has concluded that the $\Lambda$CDM timeline simply cannot accommodate the combined JWST-Planck observations even if exotic fixes are introduced to modify the standard reionization model. In this paper, we argue that this so-called `photon budget crisis' is more likely due to flaws in the cosmological model itself. We employ the standard reionization model using the JWST-measured UV luminosity function in the early Universe and the timeline and physical conditions in both $\Lambda$CDM and $R_{\rm h}=ct$. We then contrast the predicted reionization histories in these two scenarios and compare them with the data. We confirm that the reionization history predicted by $\Lambda$CDM is in significant tension with the observations, and demonstrate that the latter are instead in excellent agreement with the $R_{\rm h}=ct$ timeline. Together, the four anomalies uncovered by JWST provide strong evidence against the timeline predicted by $\Lambda$CDM and in favor of the evolutionary history in $R_{\rm h}=ct$.