Introducing the Lumina project: large-volume radiation-hydrodynamic simulations of the epochs of hydrogen and helium reionization
Abstract
Understanding how galaxies and active galactic nuclei (AGN) jointly drive the reionization of the intergalactic medium (IGM) across cosmic time remains a major challenge in cosmology. We present Lumina, a large-volume radiation-hydrodynamic simulation that self-consistently follows the coupled evolution of the intergalactic medium, galaxies, and AGN through HI, HeI, and HeII reionization down to redshift z=3. Lumina evolves a cosmological volume of comoving side length Lbox=500 cMpc with 2× 60003 resolution elements, corresponding to baryonic and dark-matter mass resolutions of 3.6× 106 M⊙ and 1.9× 107 M⊙, respectively. The simulation uses the moving-mesh code AREPO, combining the IllustrisTNG galaxy-formation model with a GPU-accelerated M1 radiation-transport solver in six frequency bins. The initial conditions employ separate transfer functions for baryons and dark matter and include their relative streaming velocity. Lumina predicts a late, predominantly stellar-driven hydrogen reionization, with the median sub-volume fully ionized by z≈ 5.2 and residual neutral HI patches persisting until z≈ 4.75. HeII reionization is driven self-consistently by AGN and is nearly complete by z=3. The simulation yields a Thomson-scattering optical depth in excellent agreement with Planck, an IGM thermal history and photoionization background broadly consistent with observational constraints, and a clear late-time thermal boost associated with HeII reionization. Its galaxy population remains consistent with the original IllustrisTNG project, while the larger volume improves statistics for rare objects, large-scale environments, and cosmic variance, enabling forward modelling of observables linking HI and HeII topologies to the evolving galaxy and AGN populations.
Versions
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BibTeX
@misc{zier2026introducing,
title = {{Introducing the Lumina project: large-volume radiation-hydrodynamic simulations of the epochs of hydrogen and helium reionization}},
author = {Oliver Zier and Aaron Smith and Xuejian Shen and Rongrong Liu and Rahul Kannan and Sonja M. Koehler and Volker Springel and Rüdiger Pakmor and Mark Vogelsberger and Teodora-Elena Bulichi and Lars Hernquist},
howpublished = {arXiv},
year = {2026},
month = aug,
doi = {10.48550/arxiv.2605.15310},
eprint = {2605.15310},
archivePrefix = {arXiv},
url = {https://arxiv.org/abs/2605.15310},
}
RIS
TY - UNPB
TI - Introducing the Lumina project: large-volume radiation-hydrodynamic simulations of the epochs of hydrogen and helium reionization
AU - Oliver Zier
AU - Aaron Smith
AU - Xuejian Shen
AU - Rongrong Liu
AU - Rahul Kannan
AU - Sonja M. Koehler
AU - Volker Springel
AU - Rüdiger Pakmor
AU - Mark Vogelsberger
AU - Teodora-Elena Bulichi
AU - Lars Hernquist
PY - 2026
DA - 2026/08/03
PB - arXiv
DO - 10.48550/arxiv.2605.15310
UR - https://arxiv.org/abs/2605.15310
AB - Understanding how galaxies and active galactic nuclei (AGN) jointly drive the reionization of the intergalactic medium (IGM) across cosmic time remains a major challenge in cosmology. We present Lumina, a large-volume radiation-hydrodynamic simulation that self-consistently follows the coupled evolution of the intergalactic medium, galaxies, and AGN through HI, HeI, and HeII reionization down to redshift z=3. Lumina evolves a cosmological volume of comoving side length L_box=500 cMpc with 2× 6000^3 resolution elements, corresponding to baryonic and dark-matter mass resolutions of 3.6× 10^6 M_⊙ and 1.9× 10^7 M_⊙, respectively. The simulation uses the moving-mesh code AREPO, combining the IllustrisTNG galaxy-formation model with a GPU-accelerated M1 radiation-transport solver in six frequency bins. The initial conditions employ separate transfer functions for baryons and dark matter and include their relative streaming velocity. Lumina predicts a late, predominantly stellar-driven hydrogen reionization, with the median sub-volume fully ionized by z≈ 5.2 and residual neutral HI patches persisting until z≈ 4.75. HeII reionization is driven self-consistently by AGN and is nearly complete by z=3. The simulation yields a Thomson-scattering optical depth in excellent agreement with Planck, an IGM thermal history and photoionization background broadly consistent with observational constraints, and a clear late-time thermal boost associated with HeII reionization. Its galaxy population remains consistent with the original IllustrisTNG project, while the larger volume improves statistics for rare objects, large-scale environments, and cosmic variance, enabling forward modelling of observables linking HI and HeII topologies to the evolving galaxy and AGN populations.
ER -