Using galactic bar dynamics to probe the nature of dark matter

暗物质是一种难以捉摸的物质，占宇宙质量的85%，是标准拉姆达冷暗物质宇宙学模型的支柱之一，它的本质仍然是现代物理学的一个主要未解之谜。虽然它的基本性质尚不清楚，但它的存在和性质可以通过它对正常（重子）物质的引力影响来推断。暗物质以两种有趣的方式与螺旋星系中的恒星相互作用：1)它稳定恒星盘，防止形成细长的旋转结构，称为星系“棒子”（例如Ostriker & Peebles 1973）； 2)当棒子形成时，暗物质对它们施加阻力，即：“动力摩擦”，导致它们减速（例如Tremaine \& Weinberg， 1984b）。由于这些过程是通过棒和暗物质粒子之间的共振相互作用介导的，因此承载棒的星系的比例以及棒的旋转速度本身将高度依赖于暗物质的存在和性质。这个博士项目将专注于使用最先进的模型，通过暗物质对螺旋星系（比如我们的银河系）的恒星和气体动力学的影响，来揭示暗物质的本质。这是特别及时的，因为我们目前生活在星系动力学的黄金时代，感谢来自盖亚和地面光谱调查的银河系和附近星系的精美数据。我们将在λ CDM和其他暗物质场景中开发和使用最先进的宇宙学模拟，以及气体动力学模型来回答以下问题：-暗物质和棒之间的共振相互作用的特征是什么？-这些特征如何取决于暗物质的性质？-不同的暗物质场景对施加在星系棒上的动力摩擦有什么影响？-在本地宇宙的螺旋星系（包括低质量和高质量）中有多少暗物质？学生将有机会开发和使用宇宙学模拟和/或气体动力学模型，并将这些模型与当前和即将到来的观测数据进行比较。

The nature of dark matter - the elusive substance making up 85\% of the mass of the Universe and one of the pillars of the standard Lambda Cold Dark Matter, cosmological model - remains a major unsolved mystery of modern physics. While its fundamental properties are as of yet unknown, its existence and properties can be inferred through its gravitational influence on normal (baryonic) matter. Dark matter interacts gravitationally with stars in spiral galaxies in two intriguing ways: i) it stabilises stellar discs against the formation of elongated, rotating structures, called galactic 'bars' (e.g. Ostriker \& Peebles 1973) and, ii) when bars do form, dark matter inflicts a drag force on them, i.e. 'dynamical friction', causing them to slow down (e.g. Tremaine \& Weinberg, 1984b). As these processes are mediated via resonant interactions between the bar and dark matter particles, the fraction of galaxies hosting bars, and the bar rotation speed itself, will be highly dependent on the existence and properties of dark matter. This PhD project will focus on using state-of-the-art models to shed light on the nature of dark matter via its effects on the stellar and gaseous dynamics of spiral galaxies, such as our own Milky Way. This is particularly timely as we are currently living in a golden era of galactic dynamics, thanks to exquisite data of the Milky Way and nearby galaxies from Gaia and ground-based spectroscopic surveys. We will develop and use state-of-the-art cosmological simulations in $\Lambda$CDM and alternative dark matter scenarios, as well as gas-dynamical models to answer questions such as: -What are the signatures of the resonant interaction between dark matter and bars? -How do these signatures depend on the nature of dark matter? -What is the effect of different dark matter scenarios on the dynamical friction exerted on galactic bars?-How much dark matter is there in spiral galaxies (both low- and high-mass) in the local Universe?The student will have the opportunity to develop and work with cosmological simulations and/or gas-dynamical models, and compare these models to current and upcoming observational data.