星系团 ZwCl0634.1+47474 中 AGN 头尾射电星系的重新能量化
Re-energisation of AGN head-tail radio galaxies in the galaxy cluster ZwCl0634.1+47474
AI总结：
本研究利用多频段射电观测分析星系团 ZwCl0634.1+4747 中的头尾射电星系，发现其尾部光谱偏离纯老化模型，证实存在湍流驱动的粒子再加速机制。
摘要：
低频射电观测显示，越来越多的位于星系团中的射电星系表现出特殊的形态和光谱轮廓。这是星系与周围介质动力学相互作用的结果。研究这一现象对于理解团内介质中低能量相对论性粒子的演化至关重要。我们对星系团 ZwCl0634.1+4747 中的三个头尾（HT）射电星系及射电晕进行了多频段研究。我们利用了 LOFAR LBA（53 MHz）、HBA（144 MHz）、GMRT（323 MHz）和 VLA（1518 MHz）在四个频率上的观测数据。使用极低射电频率观测（例如 53 和 144 MHz 的 LOFAR）使我们能够探测到尾部延伸至约 1 Mpc 的距离。我们沿尾部提取了光谱轮廓，以识别是否偏离纯老化模型，例如仅涉及同步辐射和逆康普顿损失的 Jaffe-Perola（JP）模型。我们发现了明显偏离这一简单老化模型的证据，例如所有尾部沿线的表面亮度增强和光谱变平。这可以解释为尾部沿线粒子再加速的结果。对这种行为可能的解释包括激波与射电尾部之间的相互作用，或湍流驱动的再加速机制。我们表明，后一种情景能够重现我们在光谱轮廓中观察到的特征。
英文摘要：
Low-frequency radio observations show an increasing number of radio galaxies located in galaxy clusters that display peculiar morphologies and spectral profiles. This is the result of the dynamical interaction of the galaxy with the surrounding medium. Studying this phenomenon is key to understanding the evolution of low-energy relativistic particles in the intracluster medium. We present a multi-frequency study of the three head-tail (HT) radio galaxies and the radio halo in the galaxy cluster ZwCl0634.1+4747. We make use of observations at four frequencies performed with LOFAR LBA (53 MHz), HBA (144 MHz), GMRT (323 MHz) and VLA (1518 MHz) data. The use of extremely low radio frequency observations, such as LOFAR at 53 and 144 MHz, allowed us to detect the extension of the tails up to a distance of ~ 1 Mpc. We extracted spectral profiles along the tails in order to identify possible departures from a pure ageing model, such as the Jaffe-Perola (JP) model, which only involves synchrotron and inverse-Compton losses. We found clear evidence of departures from this simple ageing model, such as surface brightness enhancement and spectral flattening along all of the tails. This can be interpreted as the consequence of particle re-acceleration along the tails. Possible explanations for this behaviour include the interaction between a shock and the radio tails or a turbulence-driven re-acceleration mechanism. We show that the latter scenario is able to reproduce the characteristic features that we observed in our profiles.
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