巨型射电遗迹的激波加速度模型

IF 1.1 4区 物理与天体物理 Q3 ASTRONOMY & ASTROPHYSICS
Hyesung Kang
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引用次数: 7

摘要

我们探索了巨型射电遗迹的激波加速模型,在该模型中,星系团外围的合并驱动激波通过扩散激波加速(DSA)加速相对论性电子。除了DSA,激波下游压缩MHD模式产生的湍流加速以及激波后电子在宇宙背景辐射中的库仑散射、同步辐射和逆康普顿散射造成的能量损失也被包括在内。考虑到只有一小部分合并星团拥有射电遗迹,我们倾向于再加速情景,即当冲击遇到含有低能($\gamma_{\rm e} \lesssim 300$)宇宙射线电子(CRe)的区域时,射电遗迹优先产生。我们利用与香肠无线电遗迹相关的物理参数对球膨胀激波进行了时间相关的DSA模拟,并计算了加速CRe的无线电同步辐射。我们发现,为了重现观测到的香肠遗迹的无线电通量密度的广泛分布,需要显著水平的激波后湍流加速度。此外,观测到的综合无线电频谱中的频谱曲率可以解释,如果假定的冲击应该在大约10万年前从化石CRe的冲击前区域扫过并退出。
本文章由计算机程序翻译,如有差异,请以英文原文为准。
Shock Acceleration Model with Postshock Turbulence for Giant Radio Relics
We explore the shock acceleration model for giant radio relics, in which relativistic electrons are accelerated via diffusive shock acceleration (DSA) by merger-driven shocks in the outskirts of galaxy clusters. In addition to DSA, turbulent acceleration by compressive MHD mode downstream of the shock is included as well as energy losses of postshock electrons by Coulomb scattering, synchrotron emission, and inverse Compton scattering off the cosmic background radiation. Considering that only a small fraction of merging clusters host radio relics, we favor the reacceleration scenario in which radio relics are generated preferentially when shocks encounter the regions containing low-energy ($\gamma_{\rm e} \lesssim 300$) cosmic ray electrons (CRe). We perform time-dependent DSA simulations of spherically expanding shocks with physical parameters relevant for the Sausage radio relic, and calculate the radio synchrotron emission from the accelerated CRe. We find that significant level of postshock turbulent acceleration is required in order to reproduce broad profiles of the observed radio flux densities of the Sausage relic. Moreover, the spectral curvature in the observed integrated radio spectrum can be explained, if the putative shock should have swept up and exited out of the preshock region of fossil CRe about 10~Myr ago.
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来源期刊
Journal of the Korean Astronomical Society
Journal of the Korean Astronomical Society 地学天文-天文与天体物理
CiteScore
1.30
自引率
10.00%
发文量
0
审稿时长
>12 weeks
期刊介绍: JKAS is an international scientific journal publishing papers in all fields of astronomy and astrophysics. All manuscripts are subject to the scrutiny of referees. Manuscripts submitted to JKAS must comply with the ethics policy of JKAS. Six regular issues are published each year on February 28, April 30, June 30, August 31, October 31, and December 31. One year''s issues compose one volume.
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