Galaxies in the first two billion years: Earlier formation and quenching with surface-density modulated star formation and feedback

@misc{vani2026galaxies,
  title = {{Galaxies in the first two billion years: Earlier formation and quenching with surface-density modulated star formation and feedback}},
  author = {Akash Vani and Mohammadreza Ayromlou and Guinevere Kauffmann and Volker Springel},
  howpublished = {arXiv},
  year = {2026},
  month = sep,
  doi = {10.48550/arxiv.2609.12060},
  eprint = {2609.12060},
  archivePrefix = {arXiv},
  url = {https://arxiv.org/abs/2609.12060},
}

TY  - UNPB
TI  - Galaxies in the first two billion years: Earlier formation and quenching with surface-density modulated star formation and feedback
AU  - Akash Vani
AU  - Mohammadreza Ayromlou
AU  - Guinevere Kauffmann
AU  - Volker Springel
PY  - 2026
DA  - 2026/09/10
PB  - arXiv
DO  - 10.48550/arxiv.2609.12060
UR  - https://arxiv.org/abs/2609.12060
AB  - JWST has revealed massive, UV-bright, compact, and in some cases quenched galaxies in the first two billion years of cosmic history, challenging current galaxy formation models. We develop an extended L-Galaxies semi-analytic model, run on the MillenniumTNG dark-matter-only simulation, and follow galaxy evolution over 0 ≤ z ≲ 15. The model ties the star formation efficiency and the coupling of stellar feedback energy to the local cold gas surface density, making star formation efficient and feedback ineffective in dense gas. We include dissipative gas-rich mergers and disc instabilities in stellar and gaseous discs. All parameters are calibrated simultaneously against stellar mass functions and quenched fractions at z≃0−4 and UV luminosity functions at z≃11−12 with a new parallelised Markov chain Monte Carlo framework. The model reproduces the stellar mass function up to z≈ 11 and increases the abundance of massive and UV-bright galaxies at z≳9 by up to two orders of magnitude over the legacy version. Although the AGN feedback prescription is unchanged, the enhanced bulge growth and black hole fuelling make massive quenched galaxies at z≃3−8 two orders of magnitude more abundant, while dissipative mergers produce compact remnants with UV size-luminosity relations matching observations at z≃10−13. At low redshift, galaxy sizes, cold-gas content, metallicities, radial profiles, and morphologies remain consistent with observations. Our results indicate that the tension between models and JWST observations at cosmic dawn can be substantially reduced by regulating star formation and feedback through the local gas surface density, without a modified initial mass function, non-standard cosmology, or new AGN physics.
ER  -