Deep XMM-Newton Observations of the NW Radio Relic Region of Abell 3667
Deep XMM-Newton Observations of the NW Radio Relic Region of Abell 3667
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阿贝尔 3667 西北射电遗迹区的深度 XMM-牛顿观测
DOI：
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发表时间：
2016
期刊：
影响因子：
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通讯作者：
T. Clarke
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文献类型：
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作者：
C. Sarazin;A. Finoguenov;D. Wik;T. Clarke
提出了对 Abell 3667 的西北射电遗迹进行长期 XMM-牛顿 X 射线观测的结果。在 X 射线表面亮度和温度分布中，都在射电遗迹的尖锐外边缘处检测到了冲击。马赫数为M = 2.54^+0.80_-0.43。激波处的温度跃变大于密度跃变的预期，这可能表明存在主要平行于激波前沿的动态重要磁场。在冲击区域内，气体温度在几个弧分钟内逐渐升高。这可能表明冲击能量最初消散为热能和非热能（例如湍流）成分的某种混合，并且非热能在冲击后区域衰减为热量。如果冲击中耗散的约 0.2% 的能量进入相对论电子的（再）加速，则观测到的射电遗迹就可以被供电。我们表明，观察到的无线电频谱随着冲击波后面距离的增加而变陡，这与无线电发射电子的辐射损失是一致的。然而，紧随激波之后的无线电频谱比热电子线性扩散激波加速的预期平坦。这表明冲击重新加速了先前存在的相对论电子群。我们还在射电遗迹的南部探测到一个明亮、凉爽的区域（“蘑菇”），我们认为它是合并子星团的残余冷核，并且该子星团是观测到的西北激波的驱动力。在此模型中，Abell 3667 的特性主要是偏移双星合并的结果，并且在第一次核心通过后约 1 Gyr 观测到该星团。我们预测，对 SE 射电遗迹进行更深入的 X 射线或 SZ 观测将揭示外缘的第二次合并激波。
The results of long XMM-Newton X-ray observations of the NW radio relic of Abell 3667 are presented. A shock is detected at the sharp outer edge of the radio relic, both in the X-ray surface brightness and the temperature profiles. The Mach number is M = 2.54^+0.80_-0.43. The temperature jump at the shock is larger than expected from the density jump, which may indicate that a dynamically important magnetic field aligned primarily parallel to the shock front is present. The gas temperature rises gradually over several arc minutes within the shock region. This could indicate that the shock energy is initially dissipated into some mix of thermal and nonthermal (e.g., turbulence) components, and that the nonthermal energy decays into heat in the post-shock region. The observed radio relic can be powered if ~0.2% of the energy dissipated in the shock goes into the (re)acceleration of relativistic electrons. We show that the observed steepening of the radio spectrum with distance behind the shock is consistent with radiative losses by the radio-emitting electrons. However, the radio spectrum immediately behind the shock is flatter than expected for linear diffusive shock acceleration of thermal electrons. This suggests that the shock re-accelerates a pre-existing population of relativistic electrons. We also detect a bright, cool region (the "Mushroom") to the south of the radio relic, which we propose is the remnant cool core of a merging subcluster, and that this subcluster was the driver for the observed NW shock. In this model, the properties of Abell 3667 are mainly the result of an offset binary merger, and the cluster is being observed about 1 Gyr after first core passage. We predict that deeper X-ray or SZ observations of the SE radio relic will reveal a second merger shock at the outer edge.