The descendants of z ≳ 10 JWST galaxies in the COLIBRE simulations

Recent observations with James Webb Space Telescope have revealed a population of UV-bright galaxies at $z\gtrsim 10$. This discovery naturally raises the question: What do such early galaxies evolve into by the present day? In this work, we address this descendant question using the new-generation COLIBRE (COLd ISM and Better REsolution) cosmological hydrodynamical simulations to trace bright galaxies selected at $z=10$ and follow their descendants to the present day. Most of the high-redshift galaxies do not survive as distinct, self-bound objects to $z=0$; instead, the majority are incorporated into more massive systems through merging or disruption. The surviving descendants span a broad range of present-day stellar masses, although they are most commonly intermediate- to high-mass, $M_\star \sim 10^{10}$–$10^{11}\, {\rm M_\odot }$. They typically reside in galaxy groups and clusters, with host halo masses, $M_{200{\rm c}}\sim 10^{13}$–$10^{14}\, {\rm M_\odot }$. The large scatter in descendant stellar mass shows that present-day outcomes retain only a weak memory of the stellar mass of the high-redshift progenitor. We show that the evolution of descendant host halo masses is consistent with the forward conditional distribution predicted by extended Press–Schechter (EPS) theory, both in the median growth and in the large scatter in descendant mass. In particular, EPS confirms that massive present-day galaxies typically do not originate from the most massive objects at high redshift. A galaxy observed at $z\gtrsim 10$ therefore cannot be interpreted as the direct progenitor of a single class of $z=0$ galaxies.