2026-04-07 京都大学
枠内イラスト：コンパス座銀河中心部のイメージ。超大質量ブラックホール（中心の黒丸）付近の高温コロナから放出された連続X線（白色）が、それを取り囲むガスと塵の層（トーラス）にあたり、さまざまな元素からの蛍光X線が発生している。（クレジット： JAXA）
背景の写真：ハッブル宇宙望遠鏡で捉えたコンパス座銀河全体の可視光画像。（クレジット：NASA、 ESA）
＜関連情報＞
- https://www.kyoto-u.ac.jp/ja/research-news/2026-04-07-0
- https://www.kyoto-u.ac.jp/sites/default/files/2026-04/web_2604_Ueda-e8cfa93bf4a67b799ca7fcd7a950ad95.pdf
- https://www.nature.com/articles/s41550-026-02817-6
超大質量ブラックホール近傍における化学組成の精密測定 Accurate determination of chemical abundances near a supermassive black hole
The XRISM Collaboration
Nature Astronomy Published:31 March 2026
DOI:https://doi.org/10.1038/s41550-026-02817-6
Abstract
The metal abundances in galactic nuclei carry key information on the history of star formation and mass transfer in central regions of galaxies. X-ray fluorescence analysis is a unique tool to reliably measure the abundances of various elements via simple physics. Here we present a new observation of the active nucleus in the Circinus galaxy with the XRISM satellite at unprecedented X-ray energy resolution. The fluorescent iron Kα line profile modified by Compton scattering indicates that the material responsible for its emission is cold and metal rich and is located ≳0.024 pc from the supermassive black hole, consistent with the dusty torus region. The abundance pattern derived from comparing fluorescent line intensities of different metals shows subsolar ratios of argon- and calcium-to-iron and a supersolar ratio of nickel-to-iron. This abundance pattern is best produced by a combination in number fraction of 92+4-2% core-collapse supernovae from progenitor stars less massive than 20+3–2M⊙ and 8+4-2% type Ia supernovae. This suggests that gas feeding the supermassive black hole was enriched by recent core-collapse supernovae. Our findings imply that in metal-rich environments stars more massive than about 20 M⊙ directly collapse into black holes or make faint supernovae without ejecting heavy metals into the space.
