宇宙の暗黒時代から初期銀河の形成までを再現する大規模シミュレーション「Lumina」（Watch the Universe Emerge From the Dark Ages, With Lumina）

2026-10-26 マサチューセッツ工科大学（MIT）

MIT、ハーバード大学などの研究チームは、ビッグバン後の初期宇宙における銀河や星の形成、宇宙の電離過程を詳細に再現する大規模シミュレーション「Lumina」を開発した。約500メガパーセク（約16億光年）の領域を対象とし、暗黒時代から約20億年間にわたる暗黒物質、ガス、星、放射の進化を追跡する。計算では約5,000億個の粒子・ガス要素を扱い、従来のIllustrisTNGシミュレーションに比べて解像度を約30倍、計算領域の体積を約100倍に拡大した。米国のスーパーコンピューター「Frontier」を利用し、銀河形成の微細な過程と宇宙規模の変化を同時に解析できる点が特徴である。シミュレーションの結果、水素の再電離は主に初期の星や銀河からの紫外線によって進み、ヘリウムの再電離は活動的な超大質量ブラックホールが放つ高エネルギー放射によって駆動されたと示された。両方の再電離過程を大規模かつ高解像度で一体的に再現したことは重要な成果である。今後、ジェームズ・ウェッブ宇宙望遠鏡などの観測結果との比較を通じて、初期銀河の形成や宇宙の大規模構造の進化を解明する研究に役立つと期待される。

A composite image of Lumina’s scales of simulation, depicting (from left to right) the streaming velocities of subatomic particles and dark matter in the beginning of simulation; gas structures during helium reionization, color-coded by how fast the gas is moving; helium reionization where blue indicates regions that are ionized by supermassive black holes; and hydrogen reionization, where bright regions show bubbles where radiation from galaxies has ionized hydrogen, while the dark regions are still neutral.Credit: Lumina collaboration

＜関連情報＞

ルミナプロジェクトの紹介：水素とヘリウムの再電離時代の大規模放射流体力学シミュレーション Introducing the lumina project: large-volume radiation-hydrodynamic simulations of the epochs of hydrogen and helium reionization

Oliver Zier , Aaron Smith , Xuejian Shen , Rongrong Liu , Rahul Kannan , Sonja M Koehler , Volker Springel , Rüdiger Pakmor , Mark Vogelsberger , Teodora-Elena Bulichi, …
Monthly Notices of the Royal Astronomical Society Published: 26 October 2026
DOI:https://doi.org/10.1093/mnras/stag1469

Abstract

Understanding how galaxies and active galactic nuclei (AGNs) 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 IGM, galaxies, and AGNs through HⅠ⁠,HeⅠ ⁠, HeⅡ and reionization down to redshift ⁠z=3. Lumina evolves a cosmological volume of comoving side length L_box=500cMpc with 2×6000³ resolution elements, corresponding to baryonic and dark matter (DM) mass resolutions of 3.6×10⁶ and ⁠1.9×10⁷M_⦿, respectively. The simulation uses the moving-mesh code arepo, combining the IllustrisTNG galaxy-formation model with a graphics processing unit-accelerated M1 radiation-transport solver in six frequency bins. The initial conditions employ separate transfer functions for baryons and DM 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 HⅠpatches persisting until z≈4.75⁠. HeⅡ reionization is driven self-consistently by AGNs 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 HeⅡreionization. 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 HⅠand HeⅡtopologies to the evolving galaxy and AGN populations.