Luminous High-Redshift Stars and Dark Matter Substructure Using Galaxy Cluster Lenses

宇宙中超过五分之四的物质是由一种不与光相互作用或不产生光的物质组成的，因此是黑暗的。尽管经过了几十年的探索，暗物质的本质仍然未知。当光线穿过或接近星系团时，它的路径会被黑暗和明亮的物质弯曲，星系团透镜可以产生多个放大的背景星系图像。在这个项目中，明尼苏达大学的科学家们将测量这些背景星系中电离气体云镜像的透镜放大倍数，以对暗物质的主要理论进行新的测试。该计划的第二个组成部分将是寻找在即将到来的大时空巡天（LSST）的成像中被高度放大的单个恒星。这些被放大的恒星在大部分可观测宇宙中都是可见的，研究它们将打开一扇新的窗口，让我们了解更年轻的宇宙。此外，这些恒星亮度的变化应该为暗物质的本质提供新的证据。在与明尼苏达大学贝尔博物馆的合作下，该团队还将为其120个座位的天文馆开发一个新的现场辅助项目，探讨围绕宇宙膨胀的过去和现在的问题。天文馆的展览将以中学生为目标，但也可以吸引成年人，它将成为贝尔博物馆日常轮换的一部分，吸引成千上万的学生和游客。研究小组将获得HII区域放大弧线镜像图像对的地基光谱。这对图像的亮度和放大倍数之间的差异一定是由暗物质亚结构引起的，因为HII区域的大尺寸意味着它们的通量不受前景星团中恒星的微透镜效应的影响。这些测量结果将与冷暗物质（CDM）和超轻玻色子暗物质的预测结果进行比较。该项目的第二个目标是研究在宇宙距离上被放大到足以被探测到的恒星。该团队将开发工具来识别LSST数据中的这些事件，并获得后续光谱和成像，以研究本地宇宙之外发光恒星的详细特性。如果星系团中存在轴子微晕，恒星的光曲线应该包含快速波动。该奖项反映了美国国家科学基金会的法定使命，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。

More than four fifths of the matter in the universe consists of a form of matter that does not interact with or produce light and is, therefore, dark. Despite decades of searches, the nature of the dark matter is not yet known. As light passes through or close to a galaxy cluster, its path is bent by both the dark and luminous matter, and cluster lenses can create multiple, magnified images of background galaxies. In this project, scientists the University of Minnesota will measure the lensing magnification of mirrored images of ionized gas clouds in these background galaxies to carry out a new test of leading theories of dark matter. A second component of the program will be to seek to identify individual stars that are highly magnified in imaging from the upcoming Large Survey of Space and Time (LSST). These magnified stars are visible across most of the observable universe and studying them will open a new window into the universe when it was much younger. Moreover, changes in these stars’ brightness should provide new evidence about the nature of dark matter. In collaboration with the University of Minnesota’s Bell Museum, the team will also develop a new live-facilitated program for its 120-seat planetarium about past and current questions surrounding the cosmic expansion. The planetarium show, which will be targeted towards middle-school students but able to engage adults, will become a part of the Bell Museum’s regular daily rotation, and reach tens of thousands of students and visitors. The research team will acquire ground-based spectroscopy of pairs of mirrored images of HII regions in magnified arcs. Differences between the brightnesses, and therefore magnifications, of these pairs of images must arise from dark-matter substructure, since the large sizes of HII regions imply that their fluxes are not affected by microlensing from stars in the foreground cluster. These measurements will be compared to predictions from both cold dark matter (CDM) and ultralight boson dark matter. The second goal of this project is to study stars at cosmological distances that are sufficiently magnified to be detected. The team will develop tools to identify these events in LSST data, and obtain follow-up spectroscopy and imaging to study the detailed properties of the luminous stars beyond the local universe. The stars’ light curves should contain rapid fluctuations if axion minihalos are present in the galaxy cluster.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.