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arXiv 1109.5871astro-ph.HEastro-ph.CO
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星系团中的Cosmic ray传输:射电晕和γ射线的意义

Cosmic ray transport in galaxy clusters: implications for radio halos and gamma-rays

Christoph Pfrommer, Torsten Ensslin, Francesco Miniati, Kandaswamy Subramanian

摘要:

对巨型射电晕的观测为星系团中宇宙线(CR)电子和磁场的存在提供了明确的证据。产生射电晕的物理机制仍有很大争议。我们批判性地讨论了无线电晕发射提出的模型,并强调每个解释的弱点。我们提出了一个想法,如何CR传播和湍流平流的相互作用选择一个双峰的空间CR分布的集群的动力学状态的特征。因此,相对于具有非常亚音速湍流的松弛簇,强烈湍流的合并簇应该具有更集中的CR能量密度分布。这转化为双峰的预期扩散无线电和伽马射线发射的集群。因此,所观察到的双峰集群无线电晕似乎是一个自然的后果CR运输过程的相互作用,独立的无线电晕形成的模型,无论是强子相互作用的CR质子或再加速的低能量CR电子。

英文摘要:

Observations of giant radio halos provide unambiguous evidence for the existence of cosmic ray (CR) electrons and magnetic fields in galaxy clusters. The physical mechanism generating radio halos is still heavily debated. We critically discuss the proposed models for the radio halo emission and highlight the weaknesses underlying each explanation. We present an idea how the interplay of CR propagation and turbulent advection selects a bimodal spatial CR distribution that is characteristic for the dynamical state of a cluster. As a result, strongly turbulent, merging clusters should have a more centrally concentrated CR energy density profile with respect to relaxed ones with very subsonic turbulence. This translates into a bimodality of the expected diffuse radio and gamma ray emission of clusters. Thus, the observed bimodality of cluster radio halos appears to be a natural consequence of the interplay of CR transport processes, independent of the model of radio halo formation, be it hadronic interactions of CR protons or re-acceleration of low-energy CR electrons.

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