论文标题

Abell 1430:与非凡的弥散无线电发射的合并群集

Abell 1430: A merging cluster with exceptional diffuse radio emission

论文作者

Hoeft, M., Dumba, C., Drabent, A., Rajpurohit, K., Rossetti, M., Nuza, S. E., van Weeren, R. J., Meusinger, H., Botteon, A., Brunetti, G., Shimwell, T. W., Cassano, R., Brüggen, M., Röttgering, H. J. A., Gastaldello, F., Lovisari, L., Yepes, G., Andrade-Santos, F., Eckert, D.

论文摘要

在许多星系簇中发现了扩散的无线电发射,主要是在合并状态的大型系统中。无线电发射通常可以分类为遗物或光晕发射,据信它们分别与合并冲击或填充湍流有关。最近的观察结果揭示了一些非常近距离的星系群的无线电桥。探索了很差的探索,可以解释相对论电子的高特异性密度的机制,这是解释这些桥梁区域的无线电发光度所必需的。我们使用详细的大量数据分析了Galaxy群集Abell 1430,并与最近的JVLA L波段观测值,XMM-Newton,Chandra和SDSS数据进行了补充。此外,我们将结果与从“三百个项目”宇宙学模拟中提取的簇进行了比较。我们发现Abell 1430由两个组件组成,即A1430-A和A1430-B。我们推测这两个组件经历了离轴合并。较大的组件显示弥漫性无线电发射,可以将其归类为无线电光环,显示出群集的质量,显示出低无线电功率。最有趣的是,具有扩展的弥漫性无线电发射,称为“枕头”,显然与A1430-B有关,因此与低密度内群内或乳层间培养基有关。迄今为止,已知源自此类地区的排放量仅有几个。这些发现对于限制可能的加速机制至关重要,这可以解释这些区域中相对论电子的存在。我们的结果表明$α_{144 \,\ text {MHz}}}^{1.5 \,\ text {ghz}} = - 1.4 \ pm0.5 $的频谱索引。如果将来的观察结果证实斜坡与-1.4甚至更平坦的中心值一样平坦,则对电子加速度方案构成巨大挑战。

Diffuse radio emission has been found in many galaxy clusters, predominantly in massive systems which are in the state of merging. The radio emission can usually be classified as relic or halo emission, which are believed to be related to merger shocks or volume-filling turbulence, respectively. Recent observations have revealed radio bridges for some pairs of very closeby galaxy clusters. The mechanisms that may allow to explain the high specific density of relativistic electrons, necessary to explain the radio luminosity of these bridge regions, are poorly explored. We analyse the galaxy cluster Abell 1430 with LoTSS data in detail and complement it with recent JVLA L-band observations, XMM-Newton, Chandra, and SDSS data. Moreover, we compare our results to clusters extracted from the "The Three Hundred Project" cosmological simulation. We find that Abell 1430 consists of two components, namely A1430-A and A1430-B. We speculate that the two components undergo an off-axis merger. The more massive component shows diffuse radio emission which can be classified as radio halo showing a low radio power given the mass of the cluster. Most interestingly, there is extended diffuse radio emission, dubbed as the `Pillow', which is apparently related to A1430-B and thus related to low density intracluster or intergalactic medium. To date, a only few examples for emission originating from such regions are known. These discoveries are crucial to constrain possible acceleration mechanisms, which may allow to explain the presence of relativistic electrons in these regions. Our results indicate a spectral index of $α_{144\,\text{MHz}}^{1.5\,\text{GHz}}=-1.4\pm0.5$ for the Pillow. If future observations confirm a slope as flat as the central value of -1.4 or even flatter, this would pose a severe challenge for the electron acceleration scenarios.

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