湍流导致的粒子再加速与对后发座星系团多信使高能辐射的射电约束
Particle Reacceleration by Turbulence and Radio Constraints on Multi-Messenger High-Energy Emission from the Coma Cluster
AI总结：
本文通过数值求解含径向扩散的Fokker–Planck方程研究湍流再加速，并结合射电与伽马射线观测约束后发座星系团的宇宙线分布及高能辐射。
摘要：
星系团被认为是宇宙线（CR）的巨大储库。已发现部分星系团存在延展射电辐射，这为星系团内介质（ICM）中磁场和CR电子的存在提供了证据。射电晕（RH）辐射机制仍存在争议，而人们普遍认为湍流再加速发挥着重要作用。本文中，我们通过数值求解Fokker–Planck方程，详细研究了CR质子和电子的再加速，并展示如何利用射电和伽马射线观测来约束后发座星系团的CR分布及其产生的高能辐射。我们考虑了CR的径向扩散，并追踪其一维分布随时间的演化，由此研究与观测到的RH表面亮度相一致的CR注入径向轮廓。我们发现，所需的注入轮廓并非显而易见，它取决于CR电子起源于原初还是次级。尽管次级CR电子情景预言了更高的伽马射线和中微子通量，但它与观测到的RH能谱存在张力。在任一情景下，我们发现如果CR能谱近乎平坦，星系团都能对全天中微子强度作出可观贡献。
英文摘要：
Galaxy clusters are considered to be gigantic reservoirs of cosmic rays (CRs). Some of the clusters are found with extended radio emission, which provides evidence for the existence of magnetic fields and CR electrons in the intra-cluster medium (ICM). The mechanism of radio halo (RH) emission is still under debate, and it has been believed that turbulent reacceleration plays an important role. In this paper, we study the reacceleration of CR protons and electrons in detail by numerically solving the Fokker-Planck equation, and show how radio and gamma-ray observations can be used to constrain CR distributions and resulting high-energy emission for the Coma cluster. We take into account the radial diffusion of CRs and follow the time evolution of their one-dimensional distribution, by which we investigate the radial profile of the CR injection that is consistent with the observed RH surface brightness. We find that the required injection profile is non-trivial, depending on whether CR electrons have the primary or secondary origin. Although the secondary CR electron scenario predicts larger gamma-ray and neutrino fluxes, it is in tension with the observed RH spectrum. In either scenario, we find that galaxy clusters can make a sizable contribution to the all-sky neutrino intensity if the CR energy spectrum is nearly flat.
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