The Galaxy Group Merger Origin of the Cloverleaf Odd Radio Circle System
E. Bulbul, X. Zhang, M.Kluge, M. Brueggen, 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

TL;DR
This paper presents the first detection of diffuse X-ray gas associated with the Cloverleaf Odd Radio Circle, suggesting it is part of a galaxy group merger and providing insights into the origin of ORCs.
Contribution
It reports the first X-ray detection of an ORC, linking it to a galaxy group merger and proposing a shock reacceleration mechanism for its radio emission.
Findings
Diffuse X-ray emission indicates a low-mass galaxy group environment.
Evidence of a galaxy group merger from optical and X-ray morphology.
Radio emission likely caused by shock reacceleration of cosmic rays.
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 cm, 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\pm 0.8) \times…
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Taxonomy
TopicsGamma-ray bursts and supernovae · Radio Astronomy Observations and Technology · History and Developments in Astronomy
