RUI: Unlocking the Origins of Ultra-Diffuse Galaxies

超扩散星系（udg）的大小与普通的螺旋星系相当，但具有矮星系般的光度。因此，它们的表面亮度极低，因此，相当数量的恒星直到最近才被编目。目前对于暗物质星系还没有一致的解释，它们令人惊讶的性质范围（例如，一些暗物质星系以暗物质为主，而另一些则完全没有暗物质）表明有多种形成途径。研究小组将通过对大量UDG样本的观测和理论结合，梳理出可能不同的UDG起源路径。本科生代表了这个研究项目的一个组成部分，并将有机会做出高影响力的发现。该项目还将与加州大学桥分校项目产生协同效应。该研究将结合8米和10米级望远镜获得的光度和光谱数据，以及在宇宙学背景下最先进的星系和星团演化模拟。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、动力结构、暗物质含量、球状星团（GC）种群和落入时间。关键项目目标包括：(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与其他矮星之间的进化联系；(4)测试无暗物质星系的新形成模型；(5)识别更多此类星系的例子。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。

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.