Too many or too bright? Status and perspectives in the study of the UV Luminosity Function at z>10

Abstract

The finding that galaxies in the first 500Myr were much more numerous and/or brighter than expected is often cited as one of the main discoveries of the James Webb Space Telescope in its first four years of operation. This result is now solidly based on an impressive number of surveys that have detected, spectroscopically confirmed, and characterized a relatively large sample of galaxies up to z=14.44, the redshift of the most distant galaxy currently known. This finding has motivated the introduction of additional physical mechanisms into theoretical models to reproduce the observed numbers and luminosities. These results contrast with the failure, despite ongoing efforts, to confirm any galaxy candidate beyond this redshift. This review summarizes the status of the search for and characterization of galaxies at z>9, focusing on the evolution of the UV Luminosity Function (UVLF), which is the main statistical description of the galaxy population that can be obtained at these redshifts. We first provide a comprehensive overview of the full set of JWST data obtained so far. We perform a 'meta--analysis' on the entire data set and provide a simple yet effective description of the global evolution of the UVLF, averaging over the various surveys. We also compare these results extensively with theoretical models that were developed to match the new JWST observations and that explore different physical mechanisms able to drive the observed evolution. We conclude with a summary of the contrasting results regarding the search for galaxy candidates at z>15, and outline the requirements for future surveys aimed at breaking this barrier.

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BibTeX RIS

BibTeX

@misc{fontana2026many,
  title = {{Too many or too bright? Status and perspectives in the study of the UV Luminosity Function at z>10}},
  author = {A. Fontana and H. Atek and V. Bromm and A. J. Bunker and M. Castellano and P. Dayal and F. D'Eugenio and D. Elbaz and A. Ferrara and S. L. Finkelstein and S. Fujimoto and M. Giavalisco and Y. Harikane and C. Kobayashi and F. Pacucci and P. G. Pérez-González and P. Rosati and A. Trinca and R. Tripodi and P. Santini and E. Vanzella and A. Venditti and A. Weibel},
  howpublished = {arXiv},
  year = {2026},
  month = oct,
  doi = {10.48550/arxiv.2610.12121},
  eprint = {2610.12121},
  archivePrefix = {arXiv},
  url = {https://arxiv.org/abs/2610.12121},
  note = {CC BY 4.0},
}

RIS

TY  - UNPB
TI  - Too many or too bright? Status and perspectives in the study of the UV Luminosity Function at z>10
AU  - A. Fontana
AU  - H. Atek
AU  - V. Bromm
AU  - A. J. Bunker
AU  - M. Castellano
AU  - P. Dayal
AU  - F. D'Eugenio
AU  - D. Elbaz
AU  - A. Ferrara
AU  - S. L. Finkelstein
AU  - S. Fujimoto
AU  - M. Giavalisco
AU  - Y. Harikane
AU  - C. Kobayashi
AU  - F. Pacucci
AU  - P. G. Pérez-González
AU  - P. Rosati
AU  - A. Trinca
AU  - R. Tripodi
AU  - P. Santini
AU  - E. Vanzella
AU  - A. Venditti
AU  - A. Weibel
PY  - 2026
DA  - 2026/10/08
PB  - arXiv
DO  - 10.48550/arxiv.2610.12121
UR  - https://arxiv.org/abs/2610.12121
AB  - The finding that galaxies in the first 500Myr were much more numerous and/or brighter than expected is often cited as one of the main discoveries of the James Webb Space Telescope in its first four years of operation. This result is now solidly based on an impressive number of surveys that have detected, spectroscopically confirmed, and characterized a relatively large sample of galaxies up to z=14.44, the redshift of the most distant galaxy currently known. This finding has motivated the introduction of additional physical mechanisms into theoretical models to reproduce the observed numbers and luminosities. These results contrast with the failure, despite ongoing efforts, to confirm any galaxy candidate beyond this redshift. This review summarizes the status of the search for and characterization of galaxies at z>9, focusing on the evolution of the UV Luminosity Function (UVLF), which is the main statistical description of the galaxy population that can be obtained at these redshifts. We first provide a comprehensive overview of the full set of JWST data obtained so far. We perform a 'meta--analysis' on the entire data set and provide a simple yet effective description of the global evolution of the UVLF, averaging over the various surveys. We also compare these results extensively with theoretical models that were developed to match the new JWST observations and that explore different physical mechanisms able to drive the observed evolution. We conclude with a summary of the contrasting results regarding the search for galaxy candidates at z>15, and outline the requirements for future surveys aimed at breaking this barrier.
ER  -

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