The Beautiful Mess in Abell 2255
The Beautiful Mess in Abell 2255
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DOI：
10.3847/1538-4357/ab9a2f
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发表时间：
2020-07-01
影响因子：
4.9
通讯作者：
Simionescu, A.
中科院分区：
文献类型：
--
作者：
Botteon, A.;Brunetti, G.;Simionescu, A.
我们目前的LOFAR观测无线电天空中最壮观的物体之一：阿贝尔2255。这是一个邻近的（z = 0.0806）合并星系团，是在团内介质（ICM）中首次发现的射电晕之一。在144 MHz的中央类似于10 Mpc（2）区域的深LOFAR图像显示了不同尺度的过多发射，从数十千秒差距到超过百万秒差距的大小。在这项工作中，我们专注于集群的最里面的区域。在观测到的众多有趣的特征中，我们发现了镶嵌在射电晕中的显着的明亮和不规则结构。我们将档案WSRT 1.2 GHz的数据来研究漫同步辐射的光谱特性，并发现一个非常复杂的光谱指数分布的光晕跨越了很宽的范围内的值。我们结合联合收割机的无线电数据与钱德拉观测研究之间的联系，通过定量比较无线电和X射线的表面亮度和无线电发射的光谱指数与ICM的物理量的热量和非热量的组件。尽管在射电晕中观察到许多结构，我们发现X射线和射电辐射总体上是相关的。最陡的光谱发射位于星系团中心，并跟踪高熵区域，这一事实可能表明存在由射电星系注入的种子粒子，这些粒子通过湍流在ICM中传播，产生扩展的射电晕。
We present LOFAR observations of one of the most spectacular objects in the radio sky: Abell 2255. This is a nearby (z = 0.0806) merging galaxy cluster hosting one of the first radio halos ever detected in the intracluster medium (ICM). The deep LOFAR images at 144 MHz of the central similar to 10 Mpc(2)region show a plethora of emission on different scales, from tens of kiloparsecs to above megaparsec sizes. In this work, we focus on the innermost region of the cluster. Among the numerous interesting features observed, we discover remarkable bright and filamentary structures embedded in the radio halo. We incorporate archival WSRT 1.2 GHz data to study the spectral properties of the diffuse synchrotron emission and find a very complex spectral index distribution in the halo spanning a wide range of values. We combine the radio data with Chandra observations to investigate the connection between the thermal and nonthermal components by quantitatively comparing the radio and X-ray surface brightness and the spectral index of the radio emission with the thermodynamical quantities of the ICM. Despite the multitude of structures observed in the radio halo, we find that the X-ray and radio emission are overall well correlated. The fact that the steepest spectrum emission is located in the cluster center and traces regions with high entropy possibly suggests the presence of seed particles injected by radio galaxies that are spread in the ICM by the turbulence generating the extended radio halo.