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”模型在匹配空间尺度大于约1Mpc的宇宙学观测方面非常成功。但是，当天文学家观察更小的尺度--即星系和星系团的尺度--时，就会出现一些问题。该模型的预测与本宇宙中观测到的低质量星系的数量、这些星系中测量到的中心质量分布以及银河系最明亮的伴星的动力学质量不一致。了解这些差异已成为国际天体物理学界的当务之急，过去5-10年在观测和理论方面都取得了重大进展。 在理论方面，新一代流体动力学模拟具有高动态范围和高质量分辨率，并对被认为对星系形成至关重要的物理过程采用越来越复杂的处理方法，正在对这个问题产生影响。在观测方面，新的仪器和望远镜正被用来研究最微弱和最小质量的恒星系统，因为这些天体对模型提供了特别严格的测试。这种研究已经产生了一些令人惊讶的现象：例如，在星系团环境中存在一些异常扩散的星系；在中等和低质量星系的中心存在大量的致密核(其中一些包含超大质量黑洞)；银晕中追踪被解体星系残骸的稀薄恒星流；在各种环境中发现的丰富的星团，其数量似乎与暗物质质量成正比；以及银河系中越来越多的“超暗”矮星系，它们似乎是宇宙中最暗物质控制的系统。 在过去的十年里，我一直是一些有史以来最大的观测项目的创始人或联合创始人，这些项目将本地宇宙作为结构形成的宇宙学模型的试验场。最先进的紫外光/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--正被用于探索两个互补环境中恒星系统的性质：室女座星系团，最近的丰富星系团和银河系的光晕。我的研究生们，他们的继续支持将成为这一计划的两个关键要素：(1)描述星系核的总质量(包括黑洞含量)、恒星形成历史和化学富集史，并建立它们与其他类型紧凑恒星系统的联系；(2)利用白矮星、蓝色水平分支恒星和贫金属星来探索晕和盘的恒星种群、结构和演化。