Shedding light on dark matter with galactic dynamics in the Milky Way and beyond

目前受欢迎的宇宙学模型(称为兰姆达冷暗物质，简称LCDM)的支柱之一是一种被称为暗物质的难以捉摸的物质，它被认为构成了宇宙的大部分质量。虽然暗物质的存在可以通过它对正常物质的引力影响来推断，比如在星系中观察到的恒星和气体，但到目前为止，它的基本性质仍然是未知的。通过引力的影响，暗物质以两种有趣的方式影响了螺旋星系盘中恒星的运动：i)它稳定了这些恒星盘，使其不受细长的旋转结构的影响，这种结构被称为星系“棒”；ii)当这样的星系棒形成时，暗物质对它们施加摩擦力，导致它们随着时间的推移旋转得更慢。由于星系棒和暗物质粒子之间的这种亲密相互作用，星系棒的性质将高度依赖于暗物质的存在和性质。因此，在星系中观察到的条状物质的性质，例如位于我们银河系核心的条状物质，可以帮助揭示暗物质的性质，从而揭示其基本性质。虽然LCDM在解释大宇宙尺度的观测方面非常成功，但当在“小”尺度，即银河系尺度上进行仔细审查时，该模型存在许多问题。此外，尽管粒子物理学家几十年来一直在寻找冷暗物质候选粒子，但到目前为止还没有发现这样的粒子。这促使该社区探索冷暗物质的替代方案，从而解决了前面提到的一些“小范围”问题。然而，对于这些不同的暗物质候选者如何影响禁止星系的动力学性质，例如我们自己的银河系，仍然缺乏定量的理论预测。此外，我们对银河系动力学结构的理解目前正在经历重大的范式转变，这要归功于来自Gaia卫星和大型地面光谱调查的出色数据。通过这个UKRI FLF，我的目标是通过利用星系棒和螺旋星系中的暗物质之间的相互作用来解开暗物质的本质，比如我们自己的银河系。这将涉及一个三管齐下的策略：首先，我将使用最先进的模型，结合来自GAIA和即将进行的4MOST和DESI等光谱调查的数据，破译银河系本身的动力学结构。其次，我将首次在另一种暗物质框架下对禁止星系的动力学性质进行理论预测。为了做到这一点，我将在这些不同的暗物质场景中开发最先进的宇宙学模拟，为恒星动力学研究量身定做。由于数值模拟的进步，使我们能够在完整的宇宙学背景下研究杆状动力学，开发这样的预测现在才成为可能。最后，我将把这些新颖的理论预测与银河系和附近其他螺旋星系的观测到的动力学结构进行比较，从而揭示暗物质的本质。

One of the pillars of the currently favoured cosmological model (called Lambda Cold Dark Matter, or LCDM), is the elusive substance known as dark matter, which is thought to make up most of the mass of the Universe. While the existence of dark matter can be inferred through its gravitational influence on normal matter -- such as the stars and gas observed in galaxies -- its fundamental nature remains, as of yet, unknown. Via its gravitational influence, dark matter affects the motions of stars in the discs of spiral galaxies in two intriguing ways: i) it stabilises these stellar discs against the formation of elongated, rotating structures, called galactic 'bars' and, ii) when such galactic bars do form, dark matter inflicts a frictional force on them, which causes them to rotate more slowly with the passage of time. Due to this intimate interplay between galactic bars and dark matter particles, the properties of bars will be highly dependent on the existence and nature of dark matter. Therefore, the observed properties of bars in galaxies, such as the one that lies at the heart of our own Milky Way, can help in revealing the properties of dark matter, thus shedding light on its fundamental nature.While LCDM has been very successful at explaining observations at large cosmological scales, the model has a number of issues when scrutinised at "small", i.e. galactic, scales. Furthermore, while particle physicists have been searching for cold dark matter candidate particles for decades, no such particle has, as of yet, been discovered. This has motivated the community to explore alternatives to cold dark matter, which resolve some of the aforementioned "small scale" issues. However, there is still a lack of quantitative theoretical predictions for how these different dark matter candidates affect the dynamical properties of barred galaxies, such as our own Milky Way. Furthermore, our understanding of the dynamical structure of our galaxy is currently undergoing a major paradigm shift, thanks to superb data from the Gaia satellite and from large ground-based spectroscopic surveys. With this UKRI FLF I aim to disentangle the nature of dark matter, by making use of the interactions between galactic bars and dark matter in spiral galaxies, such as our own Milky Way. This will involve a three-pronged strategy: Firstly, I will decipher the dynamical structure of the Milky Way itself by using state-of-the-art models, together with data from Gaia and upcoming spectroscopic surveys, such as 4MOST and DESI. Secondly, I will produce, for the first time, theoretical predictions of the dynamical properties of barred galaxies in alternative dark matter frameworks. To do this, I will develop state-of-the-art cosmological simulations in these different dark matter scenarios, tailored to stellar dynamical studies. Developing such predictions is only now becoming possible, thanks to advances in numerical simulations which allow us to study bar dynamics in the full cosmological context. Finally, I will compare these novel theoretical predictions to the observed dynamical structure of the Milky Way and other nearby spiral galaxies, thus shedding light on the nature of dark matter.