The formation and evolution of dwarf galaxies in diverse cosmological environments

冷暗物质（CDM）宇宙学模型是目前解释宇宙大尺度结构的首选范式。然而，将其小规模预测与矮星系的观测相协调提出了突出的挑战（例如Bullock和Boylan-Kolchin， 2017）。矮星系的恒星质量低于~10^9Msol，暗物质晕质量低于~10^ 11msol，它们代表了宇宙中一些最古老、暗物质占主导地位的系统，它们的浅引力势阱使它们对各种各样的内部和外部天体物理过程特别敏感。因此，它们是测试星系形成模型和流行的宇宙学预测的敏感探测器。最近，深度光学调查促进了更多更微弱的矮星系的发现，预计即将到来的维拉鲁宾天文台将大大加快新发现的速度。现有的观测已经揭示了最微弱的矮星在基本特性上的显著差异，包括它们的运动学、大小、气体含量和恒星形成历史。迄今为止，在数值模型中再现这些特性已被证明具有挑战性。此外，最微弱的矮星的形成机制仍然不确定，这在当代天体物理学的前沿提出了一个主要问题。目前的主要假设是，它们是早期宇宙的遗迹，形成于高红移，并在再电离时期被淬灭（Simon, 2019）。这篇博士论文的目的是通过使用新一代最先进的星系形成模型COLIBRE进行宇宙学放大模拟来仔细研究这一假设。COLIBRE结合了比目前最先进的星际气体物理更复杂的处理方法，此外还通过使用等质量的重子和暗物质粒子实现了卓越的动力学。因此，它非常适合研究矮星系。我们将通过创建一系列与旗舰COLIBRE运行相辅相成的模拟来研究各种环境下的矮星系：这些将是“缩放”的球形区域，从（300Mpc）^3 EAGLE-XL母体积中选择。每个都有5-10Mpc的半径（由计算限制决定），并且具有各种平均超密度，但没有大质量晕（M200 bbb10 ^12 Msol）。后一种条件降低了计算成本，并允许我们在模拟大体积的同时将每个重子粒子的分辨率提高到10^4Msol。

The lambda Cold Dark Matter (lambda CDM) cosmological model is the currently-preferred paradigm for explaining the large-scale structure of the cosmos. However, reconciling its small-scale predictions with observations of dwarf galaxies poses outstanding challenges (e.g. Bullock and Boylan-Kolchin, 2017). Classified by stellar masses below ~10^9Msol and dark matter halo masses below ~10^11 Msol, dwarf galaxies represent some of the oldest and most dark matter dominated systems in the cosmos, and their shallow gravitational potential wells make them particularly sensitive to a diverse range of internal and external astrophysical processes. They are therefore sensitive probes for testing the predictions of galaxy formation models *and* the prevailing cosmogony.Deep optical surveys have recently fostered the discovery of many more, ever-fainter, dwarf galaxies, and it is expected that the forthcoming Vera Rubin Observatory will dramatically accelerate the rate of new discoveries. Existing observations have already revealed remarkable diversity among the fundamental properties of the faintest dwarfs, including their kinematics, size, gas content and star formation histories. To date, reproducing these properties in numerical models has proven challenging. Moreover, the very formation mechanism of the faintest dwarfs remains uncertain, and poses a major question at the forefront of contemporary astrophysics. The leading hypothesis is, at present, that they are relics of the early universe, which formed at high redshift and were quenched during the epoch of reionization (Simon, 2019).This PhD thesis aims to scrutinise this hypothesis using cosmological zoom-in simulations run with the next-generation, state-of-the-art galaxy formation model: COLIBRE. COLIBRE ncorporates a more sophisticated treatment of interstellar gas physics than the current state-ofthe-art, in addition to superior dynamics achieved by using equal mass baryon and dark matter particles. It is therefore ideally suited to examination of dwarf galaxies. We will study dwarf galaxies in a diverse range of environments by creating a series of simulations complementary to the flagship COLIBRE run: these will be "zoomed" spherical regions, selected from the (300Mpc)^3 EAGLE-XL parent volume. Each will have a radius of 5-10Mpc (dictated by computational limitations), and with various mean overdensities but devoid of massive haloes (M200 > 10^12 Msol). The latter condition mitigates computational cost and allows us to increase the resolution to 10^4Msol per baryonic particle whilst still simulating a large volume.