Dwarf Galaxies and the Nature of Dark Matter

矮星系和暗物质的本质

• 批准号: RGPIN-2014-05647
• 负责人: Navarro, Julio
• 金额: $ 4.52万
• 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: 2016
• 资助国家: 加拿大
• 起止时间: 2016-01-01 至 2017-12-31
• 项目状态: 已结题
• 来源: https://www.nserc-crsng.gc.ca/ase-oro/Details-Detailles_eng.asp?id=611757
• 关键词: Dwarf; Galaxies; Nature; Dark; Matter

The past few decades have seen the emergence of a paradigm for the content and geometry of the Universe. This paradigm (usually referred to by its acronym LCDM) envisions the matter-energy content of the Universe as dominated by the evolving balance between radiation and two exotic components: cold dark matter and dark energy. However improbable this may sound, LCDM successfully accounts for most cosmological observations on large scales, and is widely regarded as the first successful cosmological theory ever devised. Its success on large scales notwithstanding, LCDM makes predictions on small scales that apparently run into conflict with observations of faint galaxies. These issues have surfaced as the completion of photometric and redshift surveys of large portions of the sky has revolutionized our understanding of faint galaxies, extending the inventory of dwarf galaxies to luminosities so faint that they blur the traditional distinction between galaxies and star clusters. These observations have highlighted potentially fatal challenges to LCDM on small scales, including the lack of a conspicuous “cusp” of dark matter at the center of dwarf galaxies; the scarcity of low-mass galaxies compared with the huge predicted abundance of low-mass dark matter halos capable, in principle, of hosting them; as well as oddities in the kinematic and spatial arrangement of the dwarf satellites of the Milky Way and Andromeda galaxies. All of these problems are the subject of active investigation, especially since plausible (but radical) modifications to the LCDM paradigm, such as “warm” or “self-interacting” dark matter, provide attractive alternatives. The confrontation of data with LCDM predictions for the smallest galaxies known thus holds the promise to validate or challenge the established paradigm on scales far removed from those used to tune its main parameters. The time seems ripe for a concerted effort designed to assess the cosmological significance of Nature's smallest extragalactic objects. I propose to study this topic using a variety of observational and theoretical tools, from detailed N-body simulation of the formation of dark matter halos, to gas-dynamical simulation of the formation of luminous dwarf galaxies, to direct observational efforts designed to survey the faintest galaxies in our Local Universe and to understand their impact on the formation of our Milky Way galaxy.

在过去的几十年里，出现了一个关于宇宙内容和几何形状的范式。这种范式（通常简称为LCDM）设想宇宙的物质能量含量由辐射和两种奇异成分（冷暗物质和暗能量）之间的平衡主导。无论这听起来多么不可能，LCDM成功地解释了大尺度上的大多数宇宙学观测，并被广泛认为是有史以来第一个成功的宇宙学理论。尽管LCDM在大尺度上取得了成功，但它在小尺度上的预测显然与暗星系的观测相冲突。这些问题已经浮出水面，因为对大部分天空的光度测量和红移测量的完成彻底改变了我们对微弱星系的理解，将矮星系的清单扩展到亮度如此微弱以至于模糊了星系和星星团之间的传统区别。这些观测结果突出了小尺度LCDM可能面临的致命挑战，包括矮星系中心缺乏明显的暗物质“尖端”;与理论上能够容纳它们的大量低质量暗物质晕相比，低质量星系的稀缺性;以及银河系和仙女座星系的矮卫星在运动学和空间排列上的古怪之处。所有这些问题都是积极研究的主题，特别是因为对LCDM范式的合理（但激进）修改，例如“温暖”或“自相互作用”暗物质，提供了有吸引力的替代方案。因此，将已知最小星系的数据与LCDM预测进行对抗，有望在与用于调整其主要参数的尺度相去甚远的尺度上验证或挑战已建立的范式。时间似乎已经成熟，可以共同努力来评估自然界最小的河外天体的宇宙学意义。我建议使用各种观测和理论工具来研究这一主题，从详细的N体模拟暗物质晕的形成，到发光矮星系形成的气体动力学模拟，再到直接观测工作，旨在调查我们本地宇宙中最微弱的星系，并了解它们对我们银河系形成的影响。