Do We Need Something Beyond Cold Dark Matter?

将星系聚集在一起的引力告诉我们，星系内部的质量比我们看到的要多--一种我们称之为“暗物质”的未知成分。 宇宙中的暗物质大约是正常物质的六倍。粒子物理项目优先级小组（P5）的最新报告将暗物质的识别列为本十年项目的关键驱动力之一。到目前为止，关于暗物质本质的唯一线索来自天文观测。有很好的证据表明暗物质必须是一种粒子，就像质子一样。事实上，可能有多个“暗”粒子（比如质子、中子、电子等）。如果是这样的话，这些暗粒子可能会相互作用，就像光与原子相互作用一样。这些相互作用可能会在星系上留下可观察到的印记。到目前为止，暗物质相互作用的模型与所有天文观测一致。在这个项目中，罗格斯大学的科学家们将对暗物质如何影响星系进行有史以来最大规模的调查。该团队将使用大量的星系模拟来研究多个独立的观测值，这些观测值可以揭示暗物质是否存在相互作用。该项目将在理解暗物质的性质方面迈出重要一步。这项工作还建立了一个计划，以支持和指导一年级的大学生（其中许多人可能来自STEM历史上代表性不足的群体），因为他们过渡到本科生。该计划将（1）发展学生和罗格斯大学物理天文学系成员之间的指导关系，（2）利用队列建设活动，将学生发展成为彼此的同伴支持网络，（3）向学生介绍基础研究工具，并让他们参与原创研究。这三个目标已被证明可以提高科学领域中代表性不足的学生的保留率。研究团队将使用一套高分辨率的最先进的模拟冷暗物质（CDM）和自相互作用暗物质（SIDM）范例中的星系形成。在CDM中运行的每个星系的初始条件将用于在SIDM中运行相同的星系，以直接比较暗物质模型的效果。该计划是：（1）检查CDM或SIDM是否可以再现在真实的星系中观察到的各种旋转曲线;（2）直接比较CDM和SIDM中观测到的星系形状;（3）测试SIDM相对于CDM的中心密度、大小和卫星的恒星剥离;（4）探索CDM和SIDM中超大质量黑洞（SMBH）的生长和合并。所提出的工作的一个战略优势是，每个测试是独立的和正交的。在项目结束时，我们对SIDM观测影响的理解将得到实质性的提高，并且对观测探测器的直接测试将确定CDM或SIDM是否是一个可行的模型。该奖项反映了NSF的法定使命，并通过使用基金会的知识价值和更广泛的影响审查标准进行评估，被认为值得支持。

The gravitational force holding galaxies together tells us that there is more mass inside galaxies than we can see — an unknown component we call “dark matter.” There is roughly six times as much dark matter as normal matter in the universe. The most recent Report of the Particle Physics Project Prioritization Panel (P5) listed the identification of dark matter as one of the key drivers of projects in this decade. So far, the only clue to the nature of dark matter has come from astronomical observations. There is good evidence that dark matter must be a particle, much like protons. In fact, there could be multiple “dark” particles (like there are protons, neutrons, electrons, etc). If that is the case, those dark particles may interact with each other, much like light interacts with atoms. These interactions could leave an observable imprint on galaxies. To date, a model with dark matter interactions is consistent with all astronomical observations. In this project, scientists at Rutgers University will undertake the largest-ever investigation into how interacting dark matter affects galaxies. The team will use a large set of galaxy simulations to study multiple, independent observables that could reveal whether dark matter has interactions or not. This project will take a major step forward in understanding the properties of dark matter. This work also establishes a program to support and mentor first-year college students (many of whom are likely to be from groups historically underrepresented in STEM) as they transition to being undergraduates. The program will (1) develop a mentoring relationship between students and members of the Rutgers Physics & Astronomy department, (2) utilize cohort building activities to develop the students into a peer support network for each other, (3) introduce the students to basic research tools and get them involved in original research. These three goals have been shown to increase the retention of underrepresented students in science.The research team will use a suite of high resolution, state-of-the art simulations of galaxy formation within both a Cold Dark Matter (CDM) and self-interacting dark matter (SIDM) paradigm. The initial conditions for every galaxy run in CDM will be used to run the same galaxy within SIDM, for a direct comparison of the effect of the dark matter model. The plan is to (1) examine whether CDM or SIDM can reproduce the diverse range of rotation curves observed in real galaxies; (2) directly compare the observed shapes of galaxies with those predicted in CDM vs SIDM; (3) test the resulting central densities, sizes, and stellar stripping of satellites in SIDM relative to CDM; (4) explore supermassive black hole (SMBH) growth and merging in CDM vs SIDM. A strategic advantage of the proposed work is that each test is independent and orthogonal. At the end of the project, our understanding of the observational impact of SIDM will be substantially improved, and direct tests against observational probes will identify whether CDM or SIDM is a viable model.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.