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arXiv · 1902.09560

Magnetic fields and extraordinarily bright radio emission in the X-ray faint galaxy group MRC 0116+111

F. Mernier·N. Werner·J. Bagchi·A. Simionescu·H. Böhringer·S. W. Allen·J. Jacob
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Abstract

MRC 0116+111 is a nearby ($z=0.132$) poor galaxy group, which was previously known for exhibiting a bright diffuse radio emission with no central point-like source, presumably related to a past activity of the active galactic nucleus (AGN) in its central cD galaxy. Here, we present an X-ray observation ($\sim$30 ks of cleaned XMM-Newton/EPIC exposure) of this system, allowing us for the first time a detailed comparison between the thermal and non-thermal components of its intragroup medium (IGrM). Remarkably, we find that the radio-to-X-ray luminosity ratio is among the highest ever observed for a diffuse extragalactic source so far, while the extent of the observed radio emission is about three times larger than its observed soft X-ray emission. Although powerful AGN activity may have disturbed the dynamics of the thermal IGrM in the form of turbulence, possibly re-energising part of the relativistic electron population, the gas properties lie within the $L_X$-$T$ scaling relation established previously for other groups. The upper limit we find for the non-thermal inverse-Compton X-ray emission translates into a surprisingly high lower limit for the volume-averaged magnetic field of the group ($\ge$4.3 $\mu$G). Finally, we discuss some interesting properties of a distant ($z \simeq 0.525$) galaxy cluster serendipitously discovered in our EPIC field of view.

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F. Mernier, N. Werner, J. Bagchi, A. Simionescu, H. Böhringer, S. W. Allen, J. Jacob. 2019-02-25. Magnetic fields and extraordinarily bright radio emission in the X-ray faint galaxy group MRC 0116+111. https://doi.org/10.1093/mnras/stz1228

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