Tracing the Dynamical States of Intracluster Media (ICMs)

宇宙在引力的作用下聚集成各种物体，小到行星、恒星，小到星系，大到星系团。研究人员将专注于了解这些星团的形成，为我们了解物体形成的整个过程提供重要的见解。星系团可以包含数百个星系，并充满了非常热的气体——它们的大气，或“星系团内介质”。这些大气非常热，它们发出的大部分光都是x射线，只有在太空中才能看到。天文学家已经证实，当一个星团剧烈碰撞并与另一个星团合并时，这种高温气体经常受到高度干扰。气体运动可以告诉我们碰撞以及这些宇宙中最大的结构是如何形成的。空间x射线望远镜追踪这些运动的能力有限，尤其是在密度较大的星团中心之外。然而，事实证明，分散在星系团中的星系喷出了高能粒子流，这些粒子流发射出从地球上可见的无线电波，揭示了它们与星系团内介质的相互作用。星系团内的气体运动也可以激发射电发射粒子，照亮运动。研究人员将利用新的和现有的地面射电望远镜观测，并利用以公民科学为基础的“射电星系动物园”，找到这些射电发射并绘制出它们的细节。此外，他们将计算详细的物理模型，以确定如何利用这些辐射来追踪星团内介质的运动以及它们的起源和历史。这些研究的结果将大大提高我们对星系团如何形成的理解。星系团是宇宙中已知的最大的引力束缚系统。它们充满了“星团内介质”，这是一种温度高达几千万度的弥漫等离子体，可以用x射线从太空中看到。研究人员将解决有关这些介质的三个关键问题：1)气体的动态状态、流动、湍流和冲击是什么？2)这些动力学特征如何帮助我们理解星团的形成过程？3)我们如何可靠地将潜在的运动与我们所能观察到的联系起来？研究人员将特别关注无线电波长下可观察到的行为，利用在磁场存在下以相对论速度运动的电子发射。这使他们能够研究星团外围等区域，而这些区域的x射线信息很少。他们将在技术前沿进行数值模拟，将高温气体的磁流体动力学与产生射电发射的相对论性粒子相结合。他们将进行最先进的射电望远镜观测和分析，并利用公民科学项目射电星系动物园的信息，研究由热气流引起的射电等离子体扭曲。总之，这项工作将使研究人员能够获得关于星团形成过程的重要信息，这是宇宙结构如何在数十亿年里发展的普遍图景的关键部分。

The universe has assembled itself by gravity into objects from the size of planets and stars up to galaxies and, on the largest scales, clusters of galaxies. The investigators will focus on understanding the formation of these clusters, giving us important insights into the entire process of how objects form. Galaxy clusters can contain hundreds of galaxies and are filled with very hot gas - their atmospheres, or "intracluster media". These atmospheres are so hot that most of the light they emit is X-rays that can be seen only from space. Astronomers have established that this hot gas has often been highly disturbed when one cluster violently collides and merges with another cluster. The gas motions can tell us about the collisions and how these largest structures in the universe form. Space X-ray telescopes are limited in their abilities to trace these motions, especially outside the denser cluster centers. As it turns out, however, galaxies scattered throughout clusters spew out streams of highly energetic particles that emit radio waves visible from the earth that reveal their interactions with the intracluster media. The intracluster gas motions can also energize radio emitting particles, illuminating the motions. The investigators will find these radio emissions and map their details, using both new and existing ground based radio telescope observations and utilizing the citizen-science-based "Radio Galaxy Zoo." In addition, they will compute detailed physical models to determine how these emissions can be used to trace out the motions of the intracluster media as well as their origins and histories. The results of these studies will substantially improve our understanding of how galaxy clusters form.Galaxy clusters are the largest known gravitationally bound systems in the universe. They are filled with 'intracluster media," diffuse plasmas with temperatures of 10s of millions of degrees, which are visible from space using X-rays. The investigators will address three key questions about these media: 1) what is the dynamical state of the gas, its flows, turbulence and shocks? 2) how do these dynamical features help us understand the cluster formation process? and 3) how do we reliably connect the underlying motions with what we can observe? The investigators will specifically concentrate on behaviors observable at radio wavelengths, using emission from electrons moving at relativistic speeds in the presence of a magnetic field. This allows them to study regimes such as cluster outskirts, for which very little X-ray information is available. They will carry out numerical simulations at the technical frontier, coupling the magnetohydrodynamics of the hot gas to the relativistic particles generating the radio emission. They will conduct new state-of-the-art radio telescope observations and analyses, along with information from the citizen science project Radio Galaxy Zoo on distortions of radio-emitting plasmas caused by the hot gas flows. Together, this work will enable the investigators to gain important information about the cluster formation process, a key piece in the universal picture of how structures in the universe develop over billions of years.