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The MillenniumTNG project: the galaxy population at z ≥ 8

Kannan, Rahul; Springel, Volker; Hernquist, Lars; Pakmor, Rüdiger; Delgado, Ana Maria; Hadzhiyska, Boryana; Hernández-Aguayo, César; Barrera, Monica; Ferlito, Fulvio; Bose, Sownak; White, Simon D M; Frenk, Carlos; Smith, Aaron; Garaldi, Enrico

The MillenniumTNG project: the galaxy population at z ≥ 8 Thumbnail


Rahul Kannan

Volker Springel

Lars Hernquist

Rüdiger Pakmor

Ana Maria Delgado

Boryana Hadzhiyska

César Hernández-Aguayo

Monica Barrera

Fulvio Ferlito

Sownak Bose

Simon D M White

Aaron Smith

Enrico Garaldi


The early release science results from JWST have yielded an unexpected abundance of high-redshift luminous galaxies that seems to be in tension with current theories of galaxy formation. However, it is currently difficult to draw definitive conclusions form these results as the sources have not yet been spectroscopically confirmed. It is in any case important to establish baseline predictions from current state-of-the-art galaxy formation models that can be compared and contrasted with these new measurements. In this work, we use the new large-volume (⁠
⁠) hydrodynamic simulation of the MillenniumTNG project, suitably scaled to match results from higher resolution – smaller volume simulations, to make predictions for the high-redshift (z ≳ 8) galaxy population and compare them to recent JWST observations. We show that the simulated galaxy population is broadly consistent with observations until z ∼ 10. From z ≈ 10–12, the observations indicate a preference for a galaxy population that is largely dust-free, but is still consistent with the simulations. Beyond z ≳ 12, however, our simulation results underpredict the abundance of luminous galaxies and their star-formation rates by almost an order of magnitude. This indicates either an incomplete understanding of the new JWST data or a need for more sophisticated galaxy formation models that account for additional physical processes such as Population III stars, variable stellar initial mass functions, or even deviations from the standard ΛCDM model. We emphasize that any new process invoked to explain this tension should only significantly influence the galaxy population beyond z ≳ 10, while leaving the successful galaxy formation predictions of the fiducial model intact below this redshift.


Kannan, R., Springel, V., Hernquist, L., Pakmor, R., Delgado, A. M., Hadzhiyska, B., …Garaldi, E. (2023). The MillenniumTNG project: the galaxy population at z ≥ 8. Monthly Notices of the Royal Astronomical Society, 524(2), 2594-2605.

Journal Article Type Article
Acceptance Date Dec 16, 2022
Online Publication Date Jul 20, 2023
Publication Date 2023-09
Deposit Date Jan 24, 2024
Publicly Available Date Jan 24, 2024
Journal Monthly Notices of the Royal Astronomical Society
Print ISSN 0035-8711
Electronic ISSN 1365-2966
Publisher Royal Astronomical Society
Peer Reviewed Peer Reviewed
Volume 524
Issue 2
Pages 2594-2605
Keywords Space and Planetary Science; Astronomy and Astrophysics
Public URL


Published Journal Article (1.9 Mb)

Copyright Statement
© 2023 The Author(s)
Published by Oxford University Press on behalf of Royal Astronomical Society

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