Matching JWST UV Luminosity Functions with Refined $Λ$CDM Halo Models
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| Formato: | Preprint |
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2025
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| _version_ | 1866908886715334656 |
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| author | Fakhry, Saeed Shiravand, Maryam Del Popolo, Antonino |
| author_facet | Fakhry, Saeed Shiravand, Maryam Del Popolo, Antonino |
| contents | The James Webb Space Telescope (JWST) has unveiled a population of unexpectedly massive and luminous galaxies at redshifts $z \gtrsim 7$, posing a significant challenge to the standard $Λ$CDM cosmological paradigm. In this work, we address the tension between early JWST observations of luminous high-redshift galaxies and predictions of the standard $Λ$CDM model by revisiting the physics of dark matter halo formation. Employing refined halo mass functions derived by Del Popolo \textit{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 $z \gtrsim 7$ compared to the conventional Sheth-Tormen (ST) formalism. Using a semi-empirical framework linking halo mass to UV luminosity, we show that the DP2 model reproduces the observed UV luminosity functions from $z = 7$ to $14$ with moderate star formation efficiencies, whereas the ST model requires implausibly high efficiencies. Our results suggest that the JWST overabundance problem stems not from new physics beyond $Λ$CDM, but from oversimplified treatments of gravitational collapse, highlighting the critical role of small-scale dissipative dynamics in early structure formation. |
| format | Preprint |
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arxiv_https___arxiv_org_abs_2510_04709 |
| institution | arXiv |
| publishDate | 2025 |
| record_format | arxiv |
| spellingShingle | Matching JWST UV Luminosity Functions with Refined $Λ$CDM Halo Models Fakhry, Saeed Shiravand, Maryam Del Popolo, Antonino Astrophysics of Galaxies Cosmology and Nongalactic Astrophysics General Relativity and Quantum Cosmology The James Webb Space Telescope (JWST) has unveiled a population of unexpectedly massive and luminous galaxies at redshifts $z \gtrsim 7$, posing a significant challenge to the standard $Λ$CDM cosmological paradigm. In this work, we address the tension between early JWST observations of luminous high-redshift galaxies and predictions of the standard $Λ$CDM model by revisiting the physics of dark matter halo formation. Employing refined halo mass functions derived by Del Popolo \textit{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 $z \gtrsim 7$ compared to the conventional Sheth-Tormen (ST) formalism. Using a semi-empirical framework linking halo mass to UV luminosity, we show that the DP2 model reproduces the observed UV luminosity functions from $z = 7$ to $14$ with moderate star formation efficiencies, whereas the ST model requires implausibly high efficiencies. Our results suggest that the JWST overabundance problem stems not from new physics beyond $Λ$CDM, but from oversimplified treatments of gravitational collapse, highlighting the critical role of small-scale dissipative dynamics in early structure formation. |
| title | Matching JWST UV Luminosity Functions with Refined $Λ$CDM Halo Models |
| topic | Astrophysics of Galaxies Cosmology and Nongalactic Astrophysics General Relativity and Quantum Cosmology |
| url | https://arxiv.org/abs/2510.04709 |