The Fossil Record of Galaxy Formation: Cosmology on Galaxy and Cluster Scales

星系形成的化石记录：星系和星团尺度的宇宙学

• 批准号: RGPIN-2017-04049
• 负责人: Cote, Patrick
• 金额: $ 2.62万
• 依托单位: University of Victoria
• 依托单位国家: 加拿大
• 项目类别: Discovery Grants Program - Individual
• 财政年份: 2020
• 资助国家: 加拿大
• 起止时间: 2020-01-01 至 2021-12-31
• 项目状态: 已结题
• 来源: https://www.nserc-crsng.gc.ca/ase-oro/Details-Detailles_eng.asp?id=710794
• 关键词: Fossil; Record; Galaxy; Formation; Cosmology

The Lambda Cold Dark Matter (CDM) "standard" model is remarkably successful in matching cosmological observations on spatial scales larger than about 1 Mpc. But when astronomers look on smaller scales -- i.e., on the scales of galaxies and galaxy clusters -- a number of problems emerge. The predictions of the model disagree with the observed numbers of low-mass galaxies in the local universe, the measured central mass distributions in those galaxies, and the dynamical masses of the Milky Way's brightest companions. Understanding these discrepancies has become a top priority for the international astrophysics community, and the last 5-10 years has seen significant progress on both the observational and theoretical fronts. In terms of theory, a new generation of hydrodynamical simulations having high dynamic range and high mass resolution, and employing increasingly sophisticated treatments of the physical processes that are believed to be important for galaxy formation, are being brought to bear on the problem. Observationally, new instruments and telescopes are being used to study the faintest and lowest-mass stellar systems, as these objects provide especially stringent tests of the models. This scrutiny has already produced some surprises: e.g., the existence of some exceptionally diffuse galaxies in cluster environments; large numbers of dense nuclei (some of which contain super-massive black holes) at the centres of intermediate- and low-mass galaxies; thin stellar streams in the Galactic halo that trace the remains of disrupted galaxies; rich populations of star clusters found in a diversity of environments whose numbers appear to scale in proportion to dark matter mass; and an ever-increasing number of "ultra faint" dwarf galaxies in the Milky Way that appear to be the most dark matter dominated systems in the universe. Over the past decade, I have been a founder, or co-founder, of some of the largest observing programs ever to use the local universe as a testing ground for cosmological models of structure formation. State-of-the-art UV/optical/IR imaging -- mainly from the Canada-France-Hawaii Telescope and the Hubble Space Telescope -- are being used, along with spectroscopy from 4-10m-class telescopes, to explore the properties of the stellar systems in two complementary environments: the Virgo Cluster, the nearest rich cluster of galaxies, and the halo of the Milky Way. My graduate students, whose continued support would be made possible with this grant, are leading two key elements of this program: (1) characterizing the total masses (including black hole content), star formation histories and chemical enrichment histories of galactic nuclei and establishing their connection to other types of compact stellar systems; and (2) using white dwarfs, blue horizontal branch stars and metal-poor stars to explore the stellar populations, structure and evolution of the halo and disk.

Lambda 冷暗物质 (CDM)“标准”模型在匹配大于约 1 Mpc 的空间尺度上的宇宙学观测方面非常成功。但是，当天文学家观察较小的尺度（即星系和星系团的尺度）时，就会出现许多问题。该模型的预测与观测到的本地宇宙中低质量星系的数量、测量到的这些星系的中心质量分布以及银河系最亮伴星的动态质量不一致。理解这些差异已成为国际天体物理学界的首要任务，过去5-10年在观测和理论方面都取得了重大进展。 从理论上讲，新一代流体动力学模拟具有高动态范围和高质量分辨率，并且对被认为对星系形成很重要的物理过程采用日益复杂的处理，正在解决这个问题。在观测方面，新的仪器和望远镜正在被用来研究最微弱和质量最低的恒星系统，因为这些物体对模型提供了特别严格的测试。这种审查已经产生了一些惊喜：例如，在星团环境中存在一些异常分散的星系；中质量和低质量星系中心有大量致密核（其中一些含有超大质量黑洞）；银河晕中的细细恒星流追踪着破碎星系的遗迹；在各种环境中发现的丰富的星团群，其数量似乎与暗物质质量成正比；银河系中越来越多的“超微弱”矮星系似乎是宇宙中暗物质主导的系统。 在过去的十年里，我是一些最大的观测项目的创始人或联合创始人，这些项目利用当地宇宙作为结构形成的宇宙学模型的试验场。正在使用最先进的紫外/光学/红外成像（主要来自加拿大-法国-夏威夷望远镜和哈勃太空望远镜）以及来自 4-10m 级望远镜的光谱来探索这些特性两个互补环境中的恒星系统：室女座星团，最近的丰富星系团，以及银河系的光环。我的研究生将通过这笔赠款获得持续的支持，他们正在领导该计划的两个关键要素：（1）表征总质量（包括黑洞含量）、恒星形成历史和星系核的化学浓缩历史，并建立它们与其他类型的紧凑恒星系统的连接； （2）利用白矮星、蓝色水平分支星和贫金属星探索星晕和星盘的星族、结构和演化。