X線天文衛星XMMニュートン、「宇宙のクローバー」に新たな光を見る(X-ray Satellite XMM-Newton Sees ’Space Clover’ in a New Light)

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2024-05-02 NASA

天文学者は一部の銀河の周囲に未知の起源の巨大な円形の電波構造を発見しました。これらの構造、通称ORC(奇妙なラジオサークル)の一つであるクローバーリーフを詳しく観測した結果、銀河団の衝突で生じたと推測されます。この新しい観測では、X線放射が初めてORCと関連付けられ、クローバーリーフの形成の秘密を解き明かす鍵となりました。研究は『Astronomy and Astrophysics Letters』に掲載されました。
ORCは非常に大きな構造で、各々が一つ以上の銀河を覆います。その強力な電波放射の原因は不明ですが、AIや新しい観測手法を活用してさらなる解明が期待されています。

<関連情報>

クローバーリーフ奇電波円系の銀河群合体起源 The galaxy group merger origin of the Cloverleaf odd radio circle system

E. Bulbul, X. Zhang, M. Kluge, M. Brüggen, B. Koribalski, A. Liu, E. Artis, Y. E. Bahar, F. Balzer, C. Garrel, V. Ghirardini, N. Malavasi, A. Merloni, K. Nandra, M. E. Ramos-Ceja, J. S. Sanders and S. Zelmer,+
Astronomy & Astrophysics  Published:30 April 2024
DOI:https://doi.org/10.1051/0004-6361/202449900

X線天文衛星XMMニュートン、「宇宙のクローバー」に新たな光を見る(X-ray Satellite XMM-Newton Sees ’Space Clover’ in a New Light)

Abstract

Odd radio circles (ORCs) are a newly discovered class of extended faint radio sources of unknown origin. We report the first detection of diffuse X-ray gas at the location of a low-redshift ORC (z = 0.046) known as Cloverleaf ORC. This observation was performed with the XMM-Newton X-ray telescope. The physical extent of the diffuse X-ray emission corresponds to a region of approximately 230 kpc by 160 kpc, lying perpendicular to the radio emission detected by ASKAP. The X-ray spectrum shows characteristics of thermal multiphase gas with temperatures of 1.10 ± 0.08 keV and 0.22 ± 0.01 keV and a central density of (4.9 ± 0.6)×10−4 cm−3, indicating that the Cloverleaf ORC resides in a low-mass galaxy group. Using X-ray observations, with hydrostatic equilibrium and isothermal assumptions, we measure the galaxy group to have a gas mass and a total mass of (7.7 ± 0.8)×1011 M and 2.6 ± 0.3 × 1013 M within the overdensity radius R500. The presence of a high-velocity subgroup identified in optical data, the orientation of the brightest cluster galaxy, the disturbed morphologies of galaxies toward the east of the Cloverleaf ORC, and the irregular morphology of the X-ray emission suggest that this system is undergoing a galaxy group merger. The radio power of the ORC could be explained by the shock reacceleration of fossil cosmic rays generated by a previous episode of black hole activity in the central active galactic nucleus.

1701物理及び化学
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