CURVED RADIO SPECTRA OF WEAK CLUSTER SHOCKS
CURVED RADIO SPECTRA OF WEAK CLUSTER SHOCKS
复制标题
弱星团激波的弯曲无线电频谱
DOI：
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发表时间：
2015
期刊：
影响因子：
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通讯作者：
D. Ryu
中科院分区：
文献类型：
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作者：
Hyesung Kang;D. Ryu
为了理解弧形巨射电遗迹的某些观测特征，如稀有性、均匀的表面亮度和弯曲的积分光谱，我们探索了一个射电遗迹的扩散激波加速（DSA）模型，其中球形激波撞击包含化石相对论电子的磁化云。为此，我们进行DSA模拟的球形冲击与相关的参数香肠无线电遗物在集群CIZA J2242.8 + 5301，并计算随后的无线电同步辐射从再加速电子。三种类型的化石电子人口被认为是：一个δ函数一样的人口与冲击注入动量，幂律分布，幂律指数截止。计算了射电辐射震后区的表面亮度剖面和体积分射电谱，并与观测结果进行了比较。我们发现，香肠遗迹的宽度可以合理地解释速度为uS = 3 × 103km s-1？和音速马赫数M s？.这些冲击产生弯曲的无线电频谱，逐渐变陡超过（0.1 - 10）br？>&ngr;具有中断频率br 1？>&ngr;如果电子加速的持续时间为1.60 - 80亿年，则为GHz。然而，在香肠遗迹中观察到的1.5 GHz以上的光谱指数的突然增加似乎表明，除了辐射损失外，还有其他物理过程对γ e = 10 4？> .
In order to understand certain observed features of arc-like giant radio relics such as the rareness, uniform surface brightness, and curved integrated spectra, we explore a diffusive shock acceleration (DSA) model for radio relics in which a spherical shock impinges on a magnetized cloud containing fossil relativistic electrons. Toward this end, we perform DSA simulations of spherical shocks with the parameters relevant for the Sausage radio relic in cluster CIZA J2242.8+5301, and calculate the ensuing radio synchrotron emission from re-accelerated electrons. Three types of fossil electron populations are considered: a delta-function like population with the shock injection momentum, a power-law distribution, and a power law with an exponential cutoff. The surface brightness profile of the radio-emitting postshock region and the volume-integrated radio spectrum are calculated and compared with observations. We find that the observed width of the Sausage relic can be explained reasonably well by shocks with speed u s ∼ 3 × 10 3 km s - 1 ?> and sonic Mach number M s ∼ 3 ?> . These shocks produce curved radio spectra that steepen gradually over (0.1–10) &ngr; br ?> with a break frequency &ngr; br ∼ 1 ?> GHz if the duration of electron acceleration is ∼60–80 Myr. However, the abrupt increase in the spectral index above ∼1.5 GHz observed in the Sausage relic seems to indicate that additional physical processes, other than radiative losses, operate for electrons with γ e ≳ 10 4 ?> .
影响因子：
4.8
作者：
F. Gasperin;R. V. Weeren;M. Brüggen;F. Vazza;A. Bonafede;H. Intema
通讯作者：
F. Gasperin;R. V. Weeren;M. Brüggen;F. Vazza;A. Bonafede;H. Intema