RUI: Unlocking the Origins of Ultra-Diffuse Galaxies

超扩散星系(UDG)在大小上与普通螺旋星系相当，但具有与星系类似的矮小亮度。因此，它们具有极低的表面亮度，因此，相当多的数字直到最近才被编目。目前对UDG还没有一致的解释，它们惊人的范围(例如，一些UDG以暗物质为主，而其他UDG似乎完全缺乏暗物质)表明有多种形成途径。研究小组将通过对大量UDG样本的观察和理论的整合，梳理出UDG起源的潜在不同路径。本科生是这项研究项目中不可或缺的一部分，他们将有机会做出有重大影响的发现。该项目还将与加州大桥计划产生协同效应。这项研究将结合用8和10M级望远镜获得的光度和光谱数据，以及在宇宙学背景下对星系和星团演化的最先进模拟。要研究的基本性质包括UDG恒星的形成历史、化学丰度模式、角动量、动力学结构、暗物质含量、球状星团(GC)种群和坠落时间。主要的项目目标包括：(1)确定富含GC和缺乏GC的UDG是否属于明显不同的家族；(2)建立不同环境下UDG之间的进化联系；(3)UDG和其他矮星之间的进化联系；(4)测试没有暗物质的星系的新形成模型；以及(5)确定更多这些星系的例子。这一奖项反映了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。

Ultra-diffuse galaxies (UDGs) are comparable in size to ordinary spirals but have dwarf galaxy-like luminosities. As a result, they possess extremely low surface brightness, and as a consequence, significant numbers have only fairly recently been cataloged. There is currently no coherent explanation for UDGs, and their surprising range of properties (e.g., some UDGs are dark matter dominated while others appear to lack dark matter altogether) suggest multiple formation pathways. The research team will tease apart potentially distinct paths of UDG origins through the integration of observations and theory for a large sample of UDGs. Undergraduate students represent an integral part of this research project and will have opportunities to make high impact discoveries. This project will also have synergies with the Cal-Bridge program. The research will combine photometric and spectroscopic data obtained with 8 and 10m-class telescopes and state-of-the-art simulations of galaxy and star cluster evolution in a cosmological context. The fundamental properties to be studied include UDG star formation histories, chemical abundance patterns, angular momentum, dynamical structure, dark matter content, globular cluster (GC) populations, and infall times. Key project goals include: (1) determining whether GC-rich and GC-poor UDGs belong to distinctly different families, (2) establishing the evolutionary connections between UDGs in different environments, (3) between UDGs and other dwarfs, (4) testing a new formation model for galaxies with no dark matter, and (5) identifying more examples of these galaxies.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.