论文标题
即使在最高频率下的完美幂律频谱：牙刷遗物
A perfect power-law spectrum even at highest frequencies: The Toothbrush relic
论文作者
论文摘要
无线电文物在集群合并期间在簇内介质（ICM）中产生的痕量冲击前线。冲击锋处的粒子加速机制尚未完全理解。我们分别在14.25 GHz和18.6 GHz的情况下观察到牙刷的遗物。与以前声称的不同，遗物的综合频谱在近三个数量频率的频率上紧密遵循了幂律，其频谱指数为$α_ {\ rm 58 \，MHz}^{\ rm 18.6 \ rm 18.6 \，ghz} = -1.16 \ pm0.03 $。正如扩散的冲击加速度理论所预测的那样，我们的发现与幂律注入频谱一致。结果表明，冲击下游只有很少的磁场强度演变。由于缺乏光谱陡峭，我们发现由压力跳跃产生的Sunyaev-Zeldovich降低要么沿$ \ sim $ 600 \，kpc沿视线范围延伸，要么是遗物位于群集中远远超过群集。我们第一次在18.6 GHz的“刷子”中检测到线性极化的发射。与8.3 GHz相比，整个刷子的极化程度在18.6 GHz时增加，表明Faraday具有强大的去极化对较低的频率。观察到的去极化与由含有湍流磁场的密集ICM产生的中间磁化屏幕一致。去极化对应于旋转度量的标准偏差，高达$σ_ {\ rm rm} = 212 \ pm23 \ rm \，rad \，rad \，m^{ - 2} $，表明刷子位于ICM中或后面。我们的发现表明，牙刷可以通过遗物形成的标准场景一致解释
Radio relics trace shock fronts generated in the intracluster medium (ICM) during cluster mergers. The particle acceleration mechanism at the shock fronts is not yet completely understood. We observed the Toothbrush relic with the Effelsberg and Sardinia Radio Telescope at 14.25 GHz and 18.6 GHz, respectively. Unlike previously claimed, the integrated spectrum of the relic closely follows a power law over almost three orders of magnitude in frequency, with a spectral index of $α_{\rm 58\,MHz}^{\rm 18.6\,GHz}=-1.16\pm0.03$. Our finding is consistent with a power-law injection spectrum, as predicted by diffusive shock acceleration theory. The result suggests that there is only little magnetic field strength evolution downstream to the shock. From the lack of spectral steepening, we find that either the Sunyaev-Zeldovich decrement produced by the pressure jump is less extended than $\sim$ 600\,kpc along the line of sight or, conversely, that the relic is located far behind in the cluster. For the first time, we detect linearly polarized emission from the "brush" at 18.6 GHz. Compared to 8.3 GHz, the degree of polarization across the brush increases at 18.6 GHz, suggesting a strong Faraday depolarization towards lower frequencies. The observed depolarization is consistent with an intervening magnetized screen that arise from the dense ICM containing turbulent magnetic fields. The depolarization, corresponding to a standard deviation of the Rotation Measures as high as $σ_{\rm RM}= 212\pm23\rm \,rad\,m^{-2}$, suggests that the brush is located in or behind the ICM. Our findings indicate that the Toothbrush can be consistently explained by the standard scenario for relic formation
