Co-Evolution of Cosmic Rays and Thermal Plasma in Galaxy Clusters

该项目将探索星系团中宇宙射线的物理和观测后果。 星系团形成于宇宙历史的早期，并且仍然通过从外围吸引物质并偶尔与其他星系团合并而不断增长。随着物质的增加，它会产生热量，就像流星在穿过地球大气层时被加热一样。与此同时，星系团中心的超大质量黑洞周围的环境以壮观的爆发方式喷出物质和能量。所有这些、热、物质和能量都注入其中的介质是等离子体--一种完全电离的气体，它非常热，不发射可见光，而是发出X射线。在这些等离子体中，大约有一百亿分之一的带电粒子是宇宙射线--能量非常大，几乎以光速传播。这个项目的目标是解开这个复杂的舞蹈质量和能量输入，了解它如何创建一个等离子体和宇宙射线的混合物，并预测它将如何出现在透镜下的无线电，x射线和伽马射线望远镜现有的和计划的未来。 该项目还将为来自传统代表性不足的群体的研究生和本科生提供研究培训。对星系团的X射线观测表明，大约40%的重子物质以普遍存在的10 - 100 keV等离子体的形式存在，称为团内介质（ICM）。ICM携带着一个具有缠结拓扑结构的磁场，并拥有能量显著的相对论宇宙射线群，这些相对论宇宙射线在无线电频率下被观察到，并有望在强子起源的伽马射线中被检测到，令人困惑的是，这从未被发现。了解ICM中的能量分配和传输，从星系团外围的全球规模引力下落和中心的超大质量黑洞活动，到在没有频繁库仑碰撞的情况下蓬勃发展的微尺度波和不稳定性，是一个多尺度非平衡等离子体物理问题。由于先进的计算资源和算法突破，几乎从第一原理开始就可以对ICM等离子体进行数值模拟，因此最近才有可能取得进展。由威斯康星州-麦迪逊大学教师领导的研究生和本科生团队与洛斯阿拉莫斯国家实验室的科学家合作，将利用这些机会首次全面模拟热等离子体、相对论宇宙射线和湍流的联合演化。计算的辐射输出预计将导致详细的预测，将通过无线电，X射线和伽马射线observations.This奖项反映了NSF的法定使命，并已被认为是值得通过使用基金会的智力价值和更广泛的影响审查标准进行评估的支持。

This project will explore the physics and observational consequences of cosmic rays in galaxy clusters. Clusters of galaxies formed early in the history of the Universe, and are still growing by pulling in matter from their outskirts and occasionally merging with other clusters. As matter is added, it creates heat, much as meteors are heated as they fall through the atmosphere of the Earth. At the same time, the environments surrounding supermassive black holes at the centers of galaxy clusters spew forth matter and energy in spectacular bursts. The medium into which all this, heat, matter, and energy are poured is a plasma – a fully ionized gas so hot that instead of emitting visible light, it glows in x-rays. About one in ten billion of the charged particles within this plasma is a cosmic ray - so energetic that it travels at nearly the speed of light. The goal of this project is to unravel this complex dance of mass and energy input, understand how it creates a plasma and cosmic ray mixture, and predict how it will appear under the lens of radio, x-ray, and gamma-ray telescopes existing now and planned for the future. The project will also provide research training for graduate and undergraduate students from traditionally under-represented groups.X-ray observations of galaxy clusters reveal that about 40% of their baryonic matter is in the form of a pervasive, 10 – 100 keV plasma known as the Intracluster Medium (ICM). The ICM carries a magnetic field with tangled topology and hosts an energetically significant population of relativistic cosmic rays, which are observed at radio frequencies and were expected to be detected in gamma-rays of hadronic origin, which puzzlingly have never been seen. Understanding energy partitioning and transport in the ICM, from global scale gravitational infall at the cluster outskirts and supermassive black hole activity at the center, to the microscale waves and instabilities that thrive in the absence of frequent Coulomb collisions, is a multi-scale non-equilibrium plasma physics problem. Progress has only recently become possible due to advanced computing resources and algorithmic breakthroughs that enable numerical simulation of ICM plasma almost from first principles. A team of graduate and undergraduate students led by faculty members at the University of Wisconsin - Madison collaborating with scientists at the Los Alamos National Laboratory will use these opportunities to comprehensively model, for the first time, the joint evolution of thermal plasma, relativistic cosmic rays, and turbulence. Radiative outputs of the calculations are expected to lead to detailed predictions that will be tested by radio, x-ray, and gamma-ray observations.This award reflects NSF's statutory mission and has been deemed worthy of support through evaluation using the Foundation's intellectual merit and broader impacts review criteria.