Ultra faint dwarf galaxies for probing the cosmological framework

用于探测宇宙学框架的超微弱矮星系

• 批准号: 2711069
• 金额: --
• 依托单位: Durham University
• 依托单位国家: 英国
• 项目类别: Studentship
• 财政年份: 2022
• 资助国家: 英国
• 起止时间: 2022 至 无数据
• 项目状态: 未结题
• 来源: https://gtr.ukri.org/projects?ref=studentship-2711069
• 关键词: Ultra; faint; dwarf; galaxies; probing

Existence of low mass dark matter halos is one of the core predictions of the concordance cosmological model, Lambda Cold Dark Matter (LCDM). Reconciling these predictions with the observations of faint (dwarf) galaxies, which inhabit the centre of these halos, has proven to be challenging for more than a decade (Bullock & Boylan-Kolchin 2017). Addressing these challenges and understanding the formation and evolution of the low mass galaxies are therefore critical for testing the validity of the cosmological framework. Thanks to the advancement of cosmological galaxy formation simulations in recent years, which follow the formation and evolution of galaxies self-consistently, some of the tensions concerning dwarf galaxies are addressed (Sales et al 2022). However these are mostly related to brighter (or "classical") dwarf galaxies. Understanding the formation and evolution of ultra faint ones still remain a major challenge in cosmological hydrodynamical simulations. The importance of studying ultra faint dwarfs is manifold. Most of these extreme objects have been discovered only recently and many more can be found with new upcoming surveys such as the Rubin Observatory. The abundance of these objects are very sensitive to the properties of dark matter particles (i.e. cold vs warm dark matter), as well as the physics of galaxy formation. Robust theoretical predictions for their abundance combined with the new observations are necessary to rule out or accept certain dark matter models. Moreover, dwarf galaxies are the most dark matter dominated galaxies in the universe and ideal places for studying the distribution of dark matter in the central parts of galaxies (aka core-cusp problem) and constrain various dark matter models, such as self-interacting dark matter. This PhD thesis aims to probe the formation of the faintest galaxies in their low mass halos with the aim of understanding the galaxy-halo connection at the faintest end and putting constraints on the abundance of these objects. The project will exploit, and develop further, some of the highest resolution cosmological simulations of dwarf galaxy formation and evolution in the LCDM framework, as part of the LYRA project (Gutcke et al. 2021,2022). In the first stage, the project will analyse the currently available simulations to investigate the galaxy and dark matter build up in these low mass systems, and in particular the dark matter distribution in the central regions. In the second stage, the project will further improve the galaxy formation model by including extra physical ingredients such as self-shielding. Then, a sample of lower mass halos will be simulated and analysed in order to probe the regime where some halos remain dark for their entire lifetime. This transition mass scale, where all halos remain dark to where all of them host a faint galaxy, is poorly constrained but has significant impact on the predicted number of ultra faint dwarfs, hence dark matter models.

低质量暗物质晕的存在是和谐宇宙学模型Lambda冷暗物质（LCDM）的核心预言之一。将这些预测与居住在这些晕中心的微弱（矮）星系的观测相结合，十多年来一直具有挑战性（布洛克& Boylan-Kolchin 2017）。因此，解决这些挑战并理解低质量星系的形成和演化对于检验宇宙学框架的有效性至关重要。由于近年来宇宙学星系形成模拟的进步，这些模拟自洽地跟踪星系的形成和演化，解决了有关矮星系的一些紧张局势（Sales et al 2022）。然而，它们大多与较亮（或“经典”）的矮星系有关。理解超暗粒子的形成和演化仍然是宇宙流体动力学模拟中的一个主要挑战。研究超暗矮星的重要性是多方面的。这些极端天体中的大多数只是最近才被发现的，更多的天体可以通过鲁宾天文台等即将进行的新调查发现。这些天体的丰度对暗物质粒子的性质（即冷暗物质与暖暗物质）以及星系形成的物理学非常敏感。对它们丰度的强有力的理论预测结合新的观测结果是排除或接受某些暗物质模型所必需的。此外，矮星系是宇宙中暗物质最占主导地位的星系，是研究星系中心暗物质分布的理想场所（又名核心尖点问题），并限制了各种暗物质模型，如自相互作用暗物质。这篇博士论文的目的是探索最暗星系在其低质量晕中的形成，目的是了解最暗端的星系晕连接，并限制这些物体的丰度。作为LYRA项目的一部分，该项目将利用并进一步发展LCDM框架中矮星系形成和演化的一些最高分辨率宇宙学模拟（Gutcke et al. 2021，2022）。在第一阶段，该项目将分析目前可用的模拟，以研究这些低质量系统中的星系和暗物质，特别是中心区域的暗物质分布。在第二阶段，该项目将进一步改进星系形成模型，包括额外的物理成分，如自屏蔽。然后，将模拟和分析低质量晕的样本，以探测某些晕在其整个寿命期间保持黑暗的状况。这种过渡质量尺度，所有的晕都保持黑暗，所有的晕都拥有一个微弱的星系，约束很差，但对超微弱矮星的预测数量有重大影响，因此暗物质模型。