Acceleration of primary and secondary particles in galaxy clusters by compressible MHD turbulence: from radio haloes to gamma-rays
Acceleration of primary and secondary particles in galaxy clusters by compressible MHD turbulence: from radio haloes to gamma-rays
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DOI：
10.1111/j.1365-2966.2010.17457.x
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发表时间：
2011-01-01
影响因子：
4.8
通讯作者：
Lazarian, A.
中科院分区：
文献类型：
--
作者：
Brunetti, G.;Lazarian, A.
射电观测发现，在受到动态扰动的星系团（射电晕）的Mpc中心区域存在大规模的非热源。这些来源的形态和光谱特性表明，发射电子的加速空间分布和温和的机制，提供了一些间接的证据，湍流加速在星系际介质（IGM）。最近已经通过伽马和射电观测获得的相对论质子在IGM的能量只有深上限。然而，这些质子应该是（理论上）IGM中的主要非热粒子成分意味着在某种程度上不可避免地产生次级粒子，这些次级粒子可能对星系团的伽马射线和射电性质产生深刻影响。本文综述了磁流体动力学理论的进展，湍流，发展一个全面的图片湍流在IGM和扩展我们以前的计算粒子加速可压缩MHD湍流考虑自洽的再加速的初级和次级粒子。在这些条件下，我们预计射电到伽马射线的发射是由星系团产生的，其复杂的光谱取决于热气体和暗物质的动力学。非热辐射结果与射电观测和目前硬X射线和伽马射线观测的限制非常一致。在我们的模型中，巨大的射电晕只在合并（湍流）集群中产生。然而，在第二次占主导地位的IGM中的电子组件的情况下，我们预计，在更轻松的集群的百万分之一规模的同步辐射的水平已经接近的无线电上限来自目前的观察集群没有无线电晕。还讨论了用现在和将来的望远镜进行观测对星系团物理的重要限制。
Radio observations discovered large-scale non-thermal sources in the central Mpc regions of dynamically disturbed galaxy clusters (radio haloes). The morphological and spectral properties of these sources suggest that the emitting electrons are accelerated by spatially distributed and gentle mechanisms, providing some indirect evidence for turbulent acceleration in the intergalactic medium (IGM).Only deep upper limits to the energy associated with relativistic protons in the IGM have been recently obtained through gamma and radio observations. Yet these protons should be (theoretically) the main non-thermal particle component in the IGM implying the unavoidable production, at some level, of secondary particles that may have a deep impact on the gamma-ray and radio properties of galaxy clusters.Following Brunetti & Lazarian, in this paper we consider the advances in the theory of magnetohydrodynamics (MHD) turbulence to develop a comprehensive picture of turbulence in the IGM and extend our previous calculations of particle acceleration by compressible MHD turbulence by considering self-consistently the re-acceleration of both primary and secondary particles. Under these conditions we expect that radio to gamma-ray emission is generated from galaxy clusters with a complex spectrum that depends on the dynamics of the thermal gas and dark matter. The non-thermal emission results in very good agreement with radio observations and with present constraints from hard X-ray and gamma-ray observations. In our model giant radio haloes are generated in merging (turbulent) clusters only. However, in case secondaries dominate the electron component in the IGM, we expect that the level of the Mpc-scale synchrotron emission in more relaxed clusters is already close to that of the radio upper limits derived by present observations of clusters without radio haloes. Important constraints on cluster physics from future observations with present and future telescopes are also discussed.