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arXiv · 2609.03537

Bright star-forming galaxies naturally forming at z>10 in the Shark semi-analytic model

Claudia D. P. Lagos·Angel Chandro-Gomez·Chris Power·Aaron S. G. Robotham
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Abstract

The James Webb Space Telescope (JWST) has unveiled the existence of numerous z>10 bright ultraviolet (UV) galaxies, potentially challenging galaxy formation models in a Lambda Cold Dark Matter (LCDM) universe. Modifications to star formation and stellar feedback models have been suggested to alleviate the tension. However, the fundamental challenge is to design a galaxy formation model that simultaneously reproduces observations from z=0 to those at the highest redshifts. Here, we present predictions from the Shark semi-analytic model of galaxy formation, which is tuned to reproduce the z=0 universe. We show that the same model is capable of reproducing the current UV luminosity function constraints even up to z=17 without the need to invoke variations in the baryon physics model. This model is also capable of reproducing reasonably well the stellar mass function evolution from z=0 to z=10 and the cosmic star formation rate (SFR) density at 0 10. We demonstrate that without this mechanism, galaxies are not bursty enough in the model to reproduce the observations at z>10.

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Claudia D. P. Lagos, Angel Chandro-Gomez, Chris Power, Aaron S. G. Robotham. 2026-09-03. Bright star-forming galaxies naturally forming at z>10 in the Shark semi-analytic model. https://arxiv.org/abs/2609.03537

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