Accelerating early massive galaxy formation with primordial black holes

Abstract

Recent observations with JWST have identified several bright galaxy candidates at $z\gtrsim 10$, some of which appear unusually massive (up to $\sim 10^{11}\ \rm M_{\odot}$). Such early formation of massive galaxies is difficult to reconcile with standard $\Lambda\rm CDM$ predictions, demanding very high star formation efficiency (SFE), possibly even in excess of the cosmic baryon mass budget in collapsed structures. With an idealized analysis based on linear perturbation theory and the Press-Schechter formalism, we show that the observed massive galaxy candidates can be explained with lower SFE than required in $\Lambda\rm CDM$, if structure formation is accelerated/seeded by massive ($\gtrsim 10^{9}\ \rm M_{\odot}$) primordial black holes (PBHs) that make a up a small fraction ($\sim 10^{-6}-10^{-3}$) of dark matter, considering existing empirical constraints on PBH parameters. We also discuss the potential observational signatures of PBH cosmologies in the JWST era. More work needs to be done to fully evaluate the viability of such PBH models to explain observations of the high-$z$ Universe.