The descendants of $z \gtrsim 10$ JWST galaxies in the COLIBRE simulations

Abstract

Recent observations with JWST 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 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, $M_\star\sim10^{10}$--$10^{11} M_\odot$. They typically reside in galaxy groups and clusters, with host halo masses, $M_{200c}\sim10^{13}$--$10^{14} M_\odot$. 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 $z\gtrsim10$ therefore cannot be interpreted as the direct progenitor of a single class of $z=0$ galaxies.