初期宇宙で成熟した銀河団を観測 （NASA Telescopes Spot Surprisingly Mature Cluster in Early Universe）

2026-01-28 NASA

＜関連情報＞

• https://www.nasa.gov/missions/chandra/nasa-telescopes-spot-surprisingly-mature-cluster-in-early-universe/
• https://www.nature.com/articles/s41586-025-09973-1

Z ≈ 5.7のX線放射原始銀河団は急速な構造成長を明らかにした An X-ray-emitting protocluster at z ≈ 5.7 reveals rapid structure growth

Ákos Bogdán,Gerrit Schellenberger,Qiong Li & Christopher J. Conselice
Nature  Published:28 January 2026
DOI:https://doi.org/10.1038/s41586-025-09973-1

Abstract

Galaxy clusters are the most massive gravitationally bound structures in the universe and serve as tracers of the assembly of large-scale structure¹. Studying their progenitors, protoclusters, sheds light on the earliest stages of cluster formation. However, detecting protoclusters is demanding: their member galaxies are loosely bound and the emerging hot intracluster medium (ICM) may only be in the initial stages of virialization^2,3,4. Recent James Webb Space Telescope (JWST) observations located several protocluster candidates by identifying overdensities of z ≳ 5 galaxies^5,6,7,8,9. However, none of these candidates was detected by X-ray observations, which offer a powerful way to unveil the hot ICM. Here we report the combined Chandra and JWST detection of a protocluster, JADES-ID1, at z ≈ 5.68, merely one billion years after the Big Bang. We measure a bolometric X-ray luminosity of L_bo1= (1.5^+0.5_-0.6)×10⁴⁴ergs^-1 and infer a total gravitating mass of M500= (1.8^+0.6_-0.7)×10¹³M_⦿, making this system a progenitor of today’s most massive galaxy clusters. The detection of extended, shock-heated gas indicates that substantial ICM heating can occur in massive halos as early as z ≈ 5.7. Also, given the limited survey volume, the discovery of such a massive cluster is statistically unlikely¹⁰, implying that the formation of the large-scale structure must have occurred more rapidly in some regions of the early universe than standard cosmological models predict.