Near-field cosmology - tagging the lowest-mass galaxies

近场宇宙学 - 标记质量最低的星系

• 批准号: ST/F010737/1
• 负责人: Andreas Koch
• 金额: $ 30.28万
• 依托单位: University of Leicester
• 依托单位国家: 英国
• 项目类别: Fellowship
• 财政年份: 2008
• 资助国家: 英国
• 起止时间: 2008 至 无数据
• 项目状态: 已结题
• 来源: https://gtr.ukri.org/projects?ref=ST%2FF010737%2F1
• 关键词: Near; field; cosmology; tagging; lowest

The formation and evolution of galaxies is a field of paramount interest in contemporary astrophysics. In this context, one key approach to the study of galaxy formation is dubbed 'near-field cosmology', that is the study of resolved stellar populations in nearby systems in and around the Milky Way. These small scale structures in the Local Group may provide some of the most challenging tests of the currently most successful cosmological models for structure formation and evolution in the Universe. This proposal aims at investigating the role of the faintest dwarf galaxies in the formation and evolution of larger galaxies. The last two years alone have seen the discovery of a dozen of these inconspicuous systems. Thus this proposal aims to study their chemical evolution, star formation histories and their dynamical properties from stellar spectroscopy. These galaxies are nowadays believed to be the fundamental building blocks of large galaxies, although this view is still controversial, as many of their properties are at variance with the stars in the Milky Way. In this work I will focus on the most recently discovered galaxies, which are the faintest, least massive and most metal poor galaxies known to date and still poorly understood. I will achieve these aims by performing chemical element abundance analyses from high-resolution spectroscopy, where I will measure abundances relative to metal poor reference stars. This will be complemented with wide-field photometry and especially medium-resolution spectroscopy. This combination will enable me to efficiently determine these galaxies' spatially resolved star formation and their enrichment histories, which then can be compared to the components of the Galaxy to understand the extent to which these small systems contributed to the build-up of the larger galaxies. The dwarf galaxies, in particular the dwarf spheroidals, are likely highly dark matter dominated systems. By investigating their kinematic properties, which I determine from radial velocity measurements from medium-resolution spectra and subsequent dynamical modeling, I can determine the galaxies' mass and density profiles, estimate their dark matter content and thus place important constraints on the properties of this evasive constituent of the Universe.

星系的形成和演化是当代天体物理学最感兴趣的领域。在这种背景下，研究星系形成的一个关键方法被称为“近场宇宙学”，即研究银河系及其周围附近系统中已分解的恒星群。局部群中的这些小尺度结构可能为目前最成功的宇宙结构形成和演化的宇宙学模型提供一些最具挑战性的测试。这一提议旨在研究最暗的矮星系在较大星系的形成和演化中所起的作用。仅在过去的两年里，就发现了十几个这样不起眼的星系。因此，这项提议旨在从恒星光谱角度研究它们的化学演化、恒星形成历史和它们的动力学性质。这些星系现在被认为是大型星系的基本组成部分，尽管这种观点仍然存在争议，因为它们的许多性质与银河系中的恒星不同。在这项工作中，我将重点介绍最近发现的星系，它们是迄今已知的最暗、质量最小、金属最贫乏的星系，但人们对它们的了解仍然很少。我将通过高分辨率光谱分析进行化学元素丰度分析来实现这些目标，在高分辨率光谱分析中，我将测量相对于贫金属参考星的丰度。这将与广域光度学，特别是中分辨率光谱学相辅相成。这种组合将使我能够有效地确定这些星系的空间分辨恒星形成及其丰富的历史，然后可以与银河系的组成部分进行比较，以了解这些小系统在多大程度上促进了更大星系的形成。矮小星系，特别是矮小椭球星系，很可能是高度暗物质控制的系统。通过研究它们的运动学性质，我从中分辨率光谱的径向速度测量和随后的动力学建模中确定了这些性质，我可以确定星系的质量和密度分布，估计它们的暗物质含量，从而对宇宙中这个难以捉摸的组成部分的性质施加重要的限制。