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所能看到的要多--这是一种未知的成分，我们称之为“暗物质”。宇宙中暗物质的数量大约是正常物质的六倍。粒子物理项目优先小组的最新报告(P5)将暗物质的识别列为本十年项目的关键驱动因素之一。到目前为止，暗物质本质的唯一线索来自天文观测。有很好的证据表明，暗物质一定是粒子，就像质子一样。事实上，可能存在多个“暗”粒子(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明显的印记。到目前为止，暗物质相互作用的模型与所有天文观测都是一致的。在这个项目中，罗格斯大学的科学家们将对相互作用的暗物质如何影响星系进行有史以来最大规模的调查。该团队将使用一大套星系模拟来研究多个独立的可观测对象，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向前迈进一大步。这项工作还建立了一个项目，以支持和指导一年级的大学生(他们中的许多人可能来自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)在学生和罗格斯大学物理与天文学系成员之间建立指导关系，(2)利用队列建设活动将学生发展成相互支持的同伴网络，(3)向学生介绍基础研究工具，并让他们参与原创研究。研究小组将使用一套高分辨率、最先进的模拟星系形成的方法来模拟冷暗物质(CDM)和自相互作用暗物质(SIDM)的星系形成。CDM中运行的每个星系的初始条件将用于运行SIDM中的同一星系，以直接比较暗物质模型的影响。该计划是：(1)检查CDM或SIDM是否能再现在真实星系中观测到的不同范围的自转曲线；(2)直接将观测到的星系形状与CDM与SIDM中预测的形状进行比较；(3)测试SIDM中卫星相对于CDM的中心密度、大小和恒星剥离；(4)探索CDM与SIDM中超大质量黑洞(SMBH)的增长和合并。拟议工作的一个战略优势是，每个测试都是独立的和正交的。在项目结束时，我们对SIDM观测影响的理解将得到显著提高，直接针对观测探测器的测试将确定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。

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.