Hunting for the First Explosions at the High-redshift Frontier

Abstract The James Webb Space Telescope (JWST) has spectroscopically confirmed galaxies up to z ∼ 14, 300 Myr after the Big Bang, and several candidates have been discovered at z ∼ 15–25, with one candidate as high as z ∼ 30, only 100 Myr after the Big Bang. Such objects are unexpected, since theoretical studies have not predicted the existence of detectable galaxies at z ∼ 30. While any z ∼ 30 candidates may be contaminants at lower redshifts, we explore whether such extreme redshift sources could be consistent with hyperenergetic transient events linked to the formation of the first, metal-free, stars. Specifically, we consider pair-instability supernovae (PISNe), a predicted class of extreme thermonuclear explosions that leave no remnant behind. Using cosmological simulations, we investigate an overdense cosmic region, where star formation and subsequent PISNe occur at z ∼ 30–40, even within standard cosmology. Assessing the likelihood of such a region, the corresponding number of PISNe at z ≳ 20, and their observed flux, we find that JWST has a nonnegligible chance of detecting a PISN event at extremely high redshifts. If a transient event were confirmed at z ∼ 30, this would provide a direct glimpse into the epoch of first star formation, dramatically extending the empirical reach of astronomy.