X射线暗星系群MRC 0116+111的磁场和异常明亮的射电辐射
Magnetic fields and extraordinarily bright radio emission in the X-ray faint galaxy group MRC 0116+111
摘要：
MRC 0116+111是一个邻近的（$z=0.132$）贫星系群，它先前以没有中心点状源的明亮弥散射电辐射而闻名，推测与其中心cD星系的活动星系核（AGN）过去的活动有关。在这里，我们提出了一个X射线观察（$\sim$ 30千像素的清洁XMM牛顿/EPIC曝光）的这个系统，让我们第一次详细比较其组内介质（IGRM）的热和非热成分。值得注意的是，我们发现，无线电X射线光度比是有史以来最高的观测到的弥漫河外源，而观测到的无线电发射的范围是约三倍，其观测到的软X射线发射。虽然强大的活动星系核活动可能以湍流的形式扰乱了热IGrM的动力学，可能重新激发了部分相对论性电子种群，但气体的性质处于先前为其他群建立的$L_X$ - $T$标度关系之内。我们发现的非热逆康普顿X射线发射的上限转化为该组的体积平均磁场的令人惊讶的高下限（$\ge$ 4.3 $μ$ G）。最后，我们讨论了一个遥远的（$z \simeq 0.525$）星系团偶然发现在我们的EPIC视野中的一些有趣的属性。
英文摘要：
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 $μ$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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