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

点击翻译按钮获取中文摘要

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.