Investigating cosmic strings using large-volume hydrodynamical simulations in the context of JWST’s massive UV-bright galaxies

¹ Institute for Theoretical Physics, Goethe University, D-60438 Frankfurt am Main, Germany
² Department of Physics, Kavli Institute for Astrophysics and Space Research, Massachusetts Institute of Technology, Cambridge, MA 02139, USA
³ Center for Astrophysics | Harvard & Smithsonian, 60 Garden Street, Cambridge, MA 02138, USA
⁴ Department of Physics, McGill University, Montréal, QC H3A 2T8, Canada
⁵ Cosmology, Gravity and Astroparticle Physics Group, Center for Theoretical Physics of the Universe, Institute for Basic Science, Daejeon 34126, Korea
⁶ Department of Physics and Astronomy, York University, 4700 Keele Street, Toronto, ON M3J 1P3, Canada

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Received: 26 November 2024
Accepted: 16 March 2026

Abstract

Recent observations from the James Webb Space Telescope (JWST) have uncovered an unexpectedly large abundance of massive, UV-bright galaxies at high redshifts, presenting a significant challenge to established galaxy formation models within the standard Lambda cold dark matter (ΛCDM) cosmological framework. Cosmic strings, predicted by a wide range of particle physics theories beyond the standard model, provide a promising potential explanation for these observations. They may act as additional gravitational seeds in the early universe, enhancing the process of high-redshift structure formation, potentially resulting in a more substantial population of massive, efficiently star-forming galaxies. We numerically investigate this prediction in large-volume hydrodynamical simulations using the moving-mesh code AREPO and the well-tested IllustrisTNG galaxy formation model. We evaluate the simulation results in the context of recent JWST data and find that sufficiently energetic cosmic strings produce UV luminosity and stellar mass functions that are in slightly to substantially better agreement with observations at high redshifts. Moreover, we observe that the halos seeded by cosmic strings exhibit a greater efficiency of star formation and enhanced central concentrations. Interestingly, our findings indicate that the simulations incorporating cosmic strings converge with those from a baseline ΛCDM model by redshift z ∼ 6. This convergence suggests that the modified cosmological framework effectively replicates the successful predictions of the standard ΛCDM model at lower redshifts, where observational constraints are significantly stronger. Our results provide compelling evidence that cosmic strings may play a crucial role in explaining the galaxy properties observed by JWST at high redshifts while maintaining consistency with well-established models at later epochs.