Discovery and Modeling of Merging Galaxy Clusters

星系团是一个巨大的实验室，承载着在数百万光年宽的舞台上上演的各种物理过程。一个特别戏剧性的过程是两个星系团碰撞并合并。因为每个星系团的大部分质量都是暗物质，所以星系团的合并就像一个“暗物质对撞机”，能够揭示暗物质粒子是如何相互作用的-这是目前没有地球实验室能做的。该团队将使用一种新技术确定合并的候选星团，然后对候选星团进行更详细的研究，以确定最简单的系统，最后对它们进行建模，以创建一个建模良好的暗物质实验室。该团队还将继续参与Cal-Bridge项目，帮助本科生获得长期支持的博士项目，并开办面向所有人的研究生招生训练营，以扩大本科生的研究机会。团队将挖掘大型光学星系团星表(目前正在使用redMaPPer，同时为未来使用更大的星系表奠定基础)，然后用X射线数据(包括档案数据和新指向的数据)研究这些候选人，以确定气体从星系中分离出来的“分离”系统。该团队将对每个解离系统进行光谱调查，以进一步评估双星；量化亚星系团之间的视线速度差异；并评估潜在的令人困惑的前景/背景结构。然后，该团队将使用引力透镜来绘制良好候选系统中的质量图，并通过从宇宙学模拟中提取类似物来对双星系统进行建模。拟议的工作包括从仅使用暗物质模拟升级到使用流体模拟，以及对激波位置的建模和观察以更好地限制合并情况。该奖项反映了NSF的法定使命，并通过使用基金会的智力优势和更广泛的影响审查标准进行评估，被认为值得支持。

A cluster of galaxies is an enormous laboratory hosting a variety of physical processes that play out on a stage millions of light-years across. A particularly dramatic process is when two clusters collide and merge. Because most of the mass of each cluster is dark matter, a cluster merger serves as a "dark matter collider" capable of revealing how dark matter particles interact with each other---something no Earthbound lab can currently do. The team will identify merging cluster candidates using a new technique, then study the candidates in greater detail to identify the simplest systems, and finally model them to create an ensemble of well-modeled dark matter laboratories. The team will also expand research opportunities for undergraduates by continuing participation in Cal-Bridge, which helps undergraduates bridge up to PhD programs with long-term support, and by running graduate admissions boot camps open to all.The team will mine large optical cluster catalogs (currently using redMaPPer while establishing a foundation for using future larger catalogs) for candidates with signs of binarity, then study those candidates with X-ray data (both archival and newly pointed) to identify "dissociative" systems where gas has separated from galaxies. The team will conduct a spectroscopic survey of each dissociative system to further assess binarity; quantify the line-of-sight velocity difference between the subclusters; and assess potentially confusing foreground/background structures. The team will then use gravitational lensing to map the mass in good candidate systems, and model binary systems by extracting analogs from cosmological simulations. The proposed work includes upgrading from using dark-matter-only simulations to using hydro simulations, and modeling and observation of shock positions to better constrain the merger scenario.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.