Radio galaxies have long been considered as potential sources of ultra-high-energy cosmic rays (UHECRs). Recent analyses of the UHECR spectrum, composition, and arrival directions indicate that the nearest radio galaxy, Centaurus A, could be linked to the reported dipole anisotropy, though the mechanism underlying the acceleration remains elusive. In this Letter, we explore UHECR acceleration in the kiloparsec-scale jets of radio galaxies, exemplified by Centaurus A. Using high-resolution relativistic magnetohydrodynamic and test-particle simulations without subgrid physics, we investigate the acceleration of the highest-energy particles in the turbulent sheath of a fast-moving jet. Our findings demonstrate that acceleration close to the maximum theoretical expectation is possible. When extrapolated to nearby radio galaxies, our results suggest that the kiloparsec-scale jets of Centaurus A could account for the dipole anisotropy in UHECRs, while more potent Fanaroff–Riley type II radio galaxies may account for the observed UHECR spectrum with a rigidity cutoff at a few Exavolts.

中文翻译：

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附近射电星系千秒差距喷流中超高能宇宙射线的加速


射电星系长期以来一直被认为是超高能宇宙射线 （UHECR） 的潜在来源。最近对 UHECR 光谱、组成和到达方向的分析表明，最近的射电星系 Centaurus A 可能与报道的偶极子各向异性有关，尽管加速背后的机制仍然难以捉摸。在这封信中，我们探讨了射电星系千秒差距喷流中的 UHECR 加速度，以 Centaurus A 为例。使用高分辨率相对论磁流体动力学和测试粒子模拟，没有子网格物理学，我们研究了最高能量粒子在快速移动的射流鞘中的加速度。我们的研究结果表明，接近最大理论期望的加速度是可能的。当外推到附近的射电星系时，我们的结果表明，半人马座 A 的千秒差距喷流可以解释 UHECR 中的偶极子各向异性，而更有效的 Fanaroff-Riley II 型射电星系可以解释观察到的 UHECR 频谱，其刚度截止为几百伏特。