Probing the Nature and Origin of Ultra Diffuse Galaxies (UDGs) with Deep and Wide-Field Imaging

超漫射星系（Ultra-diffuse galaxies, UDGs）是一种新发现的星系群。它们非常微弱，但在空间上非常延伸，几乎与夜空的亮度混合在一起。这种弥散星系是脆弱的，无法在与其他星系的引力碰撞中存活下来。然而，天文学家在星系团中发现了大量的udg，而这样的相遇可能会发生。这个研究项目将调查这些udg的性质和起源。它将研究(1)udg是否与其他类型的星系（如银河系和矮星系）不同；(2)如何保护它们免受引力干扰；(3)它们是否有更微弱的边缘。引力碰撞的影响应该在外围清晰地显现出来。这个项目将吸引各种各样的学生参与研究。该计划将使用8个本地星系团的深视场成像。这些数据是由斯巴鲁望远镜上的超级超级摄像头（HSC）拍摄的。这些独特的数据将显示出黑洞非常微弱的边缘，以及它们的大尺度环境。该计划将对集群内部、外部和集群之间的UDG人口进行最可靠的普查和解析。主要目标是：(1)确认udg在属性参数空间上是否与矮星系和正常星系不同；(2)约束它们是如何形成的，以及它们的性质如何取决于它们所处的环境；(3)对它们较暗的外围成像，并发现更暗、更广的udg。该项目主要关注udg，但旨在产生一个更广泛、连贯的图像，将udg、矮星和正常星系联系起来。udg微弱且延伸，难以检测和分析。将优化观测和数据缩减以实现这些目标。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 a newly discovered population of galaxies. They are extremely faint, but spatially very extended, and are almost blended in the brightness of the night sky. Such diffuse galaxies are fragile, and cannot survive in gravitational encounters with other galaxies. However, astronomers are finding a great number of UDGs in clusters of galaxies, where such encounters would occur. This research program will investigate the nature and origin of these UDGs. It will study (1) whether UDGs are distinct from other types of galaxies such as the Milky Way and dwarf galaxies; (2) how they are protected from the gravitational disruptions; and (3) whether they have even fainter outskirts. The effects of gravitational encounters should appear clearly in the outskirts. This project will engage a variety of students in the research.This program will use deep and wide-field imaging of eight local clusters of galaxies. The data are taken with the Hyper Suprime-Cam (HSC) on the Subaru telescope. These unique data will show the very faint outskirts of UDGs, as well as their large-scale environments. The program will perform the most reliable census and resolved analysis of the UDG population within, outside, and among the clusters. The main goals are (1) to confirm whether UDGs are distinct from dwarf and normal galaxies in their properties parameter spaces; (2) to constrain how they formed and how they their properties depend on their environments; and (3) to image their fainter outskirts and to discover even fainter, more extended UDGs. The project focuses primarily on UDGs, but aims to yield a broader, coherent picture that connects UDGs, dwarfs, and normal galaxies. UDGs are faint and extended, and are difficult to be detected and analyzed. The observations and data reduction will be optimized to achieve these goals.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.