2025-04-22 自然科学研究機構
図1:ペルセウス座銀河団で検出されたダークマターの分布(青色)。背景はすばる望遠鏡の HSC で撮影された画像です。研究チームは、背景にある銀河の形がペルセウス座銀河団のダークマターの存在によってごくわずかに歪められる影響(弱重力レンズ効果)を精密測定して、ダークマターの分布を調べました。本研究で発見されたダークマターの塊(副構造)は銀河団中心部(主構造)から約 140 万光年離れた位置にあります。さらに、副構造と主構造を結ぶ橋のような構造も発見されました。(クレジット:HyeongHan et al.)
<関連情報>
- https://subarutelescope.org/jp/results/2025/04/22/3545.html
- https://www.nature.com/articles/s41550-025-02530-w
ペルセウス座銀河団における大合併の直接証拠 Direct evidence of a major merger in the Perseus cluster
Kim HyeongHan,M. James Jee,Wonki Lee,John ZuHone,Irina Zhuravleva,Wooseok Kang & Ho Seong Hwang
Nature Astronomy Published:16 April 2025
DOI:https://doi.org/10.1038/s41550-025-02530-w
Abstract
Although the Perseus cluster has often been regarded as an archetypical relaxed galaxy cluster, several lines of evidence, including ancient, large-scale cold fronts, asymmetric plasma morphology, filamentary galaxy distribution and so on, provide a conflicting view of its dynamical state, suggesting that the cluster might have experienced a major merger. However, the absence of a clear merging companion identified so far hampers our understanding of the evolutionary track of the Perseus cluster consistent with these observational features. Here, through careful weak-lensing analysis, we successfully identified the missing subcluster halo (total mass M200=1.70+0.73−0.59×1014M⊙) at the >5σ level centred on NGC 1264, which is located ~430 kpc west of the Perseus main cluster core. Moreover, a significant (>3σ) mass bridge, which is also traced by the cluster member galaxies, is detected between the Perseus main and subclusters, which serves as direct evidence of gravitational interaction. With idealized numerical simulations, we demonstrate that an ~3:1 off-axis major merger can create the cold front observed ~700 kpc east of the main cluster core and generate the observed mass bridge through multiple core crossings. This discovery resolves the long-standing puzzle of Perseus’s dynamical state.