The galaxy ultraviolet luminosity function from z = 7 to 20 in the COLIBRE simulations
10 affiliations
- 1Institute for Computational Cosmology, Department of Physics, University of Durham , South Road, Durham DH1 3LE ,
- 2Department of Physics and Astronomy, Universiteit Gent , Proeftuinstraat 86 N3, B-9000 Ghent ,
- 3Leiden Observatory, Leiden University , PO Box 9513, NL-2300 RA Leiden ,
- 4Astrophysics Research Institute, Liverpool John Moores University , 146 Brownlow Hill, Liverpool L3 5RF ,
- 5Dipartimento di Fisica G. Occhialini, Università degli Studi di Milano Bicocca, Piazza della Scienza , 3 I-20126 Milano MI ,
- 6Department of Astrophysics, University of Vienna , Türkenschanzstrasse 17, A-1180 Vienna ,
- 7Centre for Data Science, Artificial Intelligence and Modelling, University of Hull , Cottingham Road, Hull HU6 7RX ,
- 8E. A. Milne Centre for Astrophysics, University of Hull , Cottingham Road, Hull HU6 7RX ,
- 9Lorentz Institute for Theoretical Physics, Leiden University , PO Box 9506, NL-2300 RA Leiden ,
- 10Centre for Astrophysics Research, Department of Physics, Astronomy and Mathematics, University of Hertfordshire , College Lane, Hatfield, AL10 9AB ,
Abstract
James Webb Space Telescope (JWST) has enabled the detection of galaxies in the earliest stages of cosmic history. We compare the ultraviolet luminosity functions (UVLFs) at redshifts z=7−20 predicted by a set of new cosmological hydrodynamical simulations, colibre (COLd ISM and Better REsolution), with observations, including those from JWST. The UV luminosities of colibre galaxies are derived using the radiative transfer code skirt, which tracks stellar emission and its processing through the multiphase interstellar medium and dust distribution predicted by colibre. We find that although colibre is consistent with the observed evolution of the stellar mass function up to z=12, its dust-attenuated UVLFs fall systematically below the observations at the bright end: at the number density of 10−6 Mpc−3 mag−1, the brightest galaxies are underluminous by ≈ 1 mag at z=7, increasing to ≈ 2.5 mag at z=15. Accounting for observational uncertainties brings the colibre UVLFs closer to the observational data, but does not fully resolve the discrepancy. Ignoring dust attenuation allows colibre to produce sufficiently bright galaxies at 7≲ z ≲ 12, but at z=15, colibre still underpredicts the luminosities of the brightest galaxies, indicating the need for additional physical mechanisms to boost the UV luminosities at the earliest cosmic epochs, such as a ‘top-heavy’ stellar initial mass function. We fit the colibre UVLFs with Schechter functions and calculate the evolution of the best-fitting parameters. We find that the galaxy number density decreases, the characteristic luminosity becomes fainter and the faint-end slope becomes steeper towards higher redshifts. The UV luminosity density decreases by a factor of several hundred from z = 7 to $15$.
Versions
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BibTeX
@article{lu2026galaxy,
title = {{The galaxy ultraviolet luminosity function from z = 7 to 20 in the COLIBRE simulations}},
author = {Shengdong Lu and Carlos S Frenk and Cedric G Lacey and Andrea Gebek and Joop Schaye and Shaun Cole and Sownak Bose and Anna Durrant and Nick Andreadis and Maarten Baes and Alejandro Benítez-Llambay and Evgenii Chaikin and Camila Correa and Robert A Crain and Filip Huško and Robert J McGibbon and Sylvia Ploeckinger and Alexander J Richings and Matthieu Schaller and James W Trayford},
journal = {Monthly Notices of the Royal Astronomical Society},
year = {2026},
month = sep,
doi = {10.1093/mnras/stag1846},
url = {https://academic.oup.com/mnras/article/doi/10.1093/mnras/stag1846/8855712},
note = {CC BY 4.0},
}
RIS
TY - JOUR
TI - The galaxy ultraviolet luminosity function from z = 7 to 20 in the COLIBRE simulations
AU - Shengdong Lu
AU - Carlos S Frenk
AU - Cedric G Lacey
AU - Andrea Gebek
AU - Joop Schaye
AU - Shaun Cole
AU - Sownak Bose
AU - Anna Durrant
AU - Nick Andreadis
AU - Maarten Baes
AU - Alejandro Benítez-Llambay
AU - Evgenii Chaikin
AU - Camila Correa
AU - Robert A Crain
AU - Filip Huško
AU - Robert J McGibbon
AU - Sylvia Ploeckinger
AU - Alexander J Richings
AU - Matthieu Schaller
AU - James W Trayford
PY - 2026
DA - 2026/09/30
JO - Monthly Notices of the Royal Astronomical Society
DO - 10.1093/mnras/stag1846
UR - https://academic.oup.com/mnras/article/doi/10.1093/mnras/stag1846/8855712
AB - James Webb Space Telescope (JWST) has enabled the detection of galaxies in the earliest stages of cosmic history. We compare the ultraviolet luminosity functions (UVLFs) at redshifts z=7−20 predicted by a set of new cosmological hydrodynamical simulations, colibre (COLd ISM and Better REsolution), with observations, including those from JWST. The UV luminosities of colibre galaxies are derived using the radiative transfer code skirt, which tracks stellar emission and its processing through the multiphase interstellar medium and dust distribution predicted by colibre. We find that although colibre is consistent with the observed evolution of the stellar mass function up to z=12, its dust-attenuated UVLFs fall systematically below the observations at the bright end: at the number density of 10^−6 Mpc^−3 mag^−1, the brightest galaxies are underluminous by ≈ 1 mag at z=7, increasing to ≈ 2.5 mag at z=15. Accounting for observational uncertainties brings the colibre UVLFs closer to the observational data, but does not fully resolve the discrepancy. Ignoring dust attenuation allows colibre to produce sufficiently bright galaxies at 7≲ z ≲ 12, but at z=15, colibre still underpredicts the luminosities of the brightest galaxies, indicating the need for additional physical mechanisms to boost the UV luminosities at the earliest cosmic epochs, such as a ‘top-heavy’ stellar initial mass function. We fit the colibre UVLFs with Schechter functions and calculate the evolution of the best-fitting parameters. We find that the galaxy number density decreases, the characteristic luminosity becomes fainter and the faint-end slope becomes steeper towards higher redshifts. The UV luminosity density decreases by a factor of several hundred from z = 7 to $15$.
SN - 0035-8711
SN - 1365-2966
ER -