Matching JWST Ultraviolet Luminosity Functions with Refined ΛCDM Halo Models

Abstract The James Webb Space Telescope (JWST) has unveiled a population of unexpectedly massive and luminous galaxies at redshifts z ≳ 7, posing a significant challenge to the standard Lambda cold dark matter (ΛCDM) cosmological paradigm. In this work, we address the tension between early JWST observations of luminous high-redshift galaxies and predictions of the standard ΛCDM model by revisiting the physics of dark matter halo formation. Employing refined halo mass functions derived by A. Del Popolo et al. (DP1 and DP2) that incorporate angular momentum, dynamical friction, and redshift-dependent collapse barriers, we demonstrate a significant enhancement in the abundance of massive halos at z ≳ 7 compared to the conventional Sheth–Tormen (ST) formalism. Using a semiempirical framework linking halo mass to UV luminosity, we show that the DP2 model reproduces the observed UV luminosity functions (UVLFs) from z = 7 to 14 with moderate star formation efficiencies, whereas the ST model requires implausibly high efficiencies. A normalized reduced χ 2 analysis quantitatively confirms that the DP2 model provides the best statistical match to the JWST UVLF data in the vast majority of redshift bins. Our results suggest that the JWST overabundance problem stems not from new physics beyond ΛCDM, but from oversimplified treatments of gravitational collapse, highlighting the critical role of small-scale dissipative dynamics in early structure formation.