2025MNRAS.539.1796L

In this paper, we describe our search for galaxy protocluster candidates at $4.5{<} z {<} 10$ and explore the environmental and physical properties of their member galaxies identified through JWST wide-field surveys within the CEERS (Cosmic Evolution Early Release Science), JADES (JWST Advanced Deep Extragalactic Survey), and PEARLS (Prime Extragalactic Areas for Reionization and Lensing Science) NEP-TDF (North Ecliptic Pole Time-Domain Fields). Combining with Hubble Space Telescope (HST) data, we identify 2948 robust $z>4.5$ galaxy candidates within an area of 185.4 arcmin$^2$. We determine nearest neighbour statistics and galaxy environments. We find that high-z galaxies in overdense environments exhibit higher star formation activity compared to those in underdense regions. Galaxies in dense environments have a slightly increased star formation rate (SFR) at a given mass compared with galaxies in the lower density environments. At the high-mass end, we also find a gradual flattening of the $M_{\star }$-SFR slope. We find that galaxies in high-density regions often have redder ultraviolet slopes than those in low-density regions, suggesting more dust extinction, weaker Ly α emission, and/or a higher damped Ly α absorption. The mass-size relation shows a weak positive correlation between galaxy size and local density. Furthermore, we quantitatively assess the probability of a galaxy belonging to a protocluster candidate. In total, we identified 26 overdensities at $z=5{\!-\!}7$ and estimate their dark matter halo masses. We find that all proto-cluster candidates could evolve into clusters with $M_{\rm halo} > 10^{14}{\rm M}_{\odot }$ at $z = 0$, thereby supporting the theoretical and simulation predictions of cluster formation. Notably, this marks an early search for protocluster candidates in JWST wide field based on photometric data, providing valuable candidates to study cosmic structure formation at the early stages.