Probing Cosmology with ultra faint dwarf galaxies

我的研究重点是探索物理学和宇宙学中的基本未知之一：神秘的“暗物质”，占宇宙物质的80%。暗物质的性质尚不清楚，但它在星系和星系团中的证据已经通过其对物质和光的引力影响被观察到;例如影响星系中恒星的运动。根据目前的宇宙学模型，星系居住在更扩展的暗物质晕的中心。低质量星系（矮星系）和它们的暗物质晕（超暗矮星或UFD）被认为比星系本身质量大得多。因此，矮星系和UFD是探索暗物质性质的绝佳实验室。然而，由于它们的低质量和微弱的性质，对这些物体的研究在观测和理论上都具有挑战性。大多数已知的UFD都是在最近几年才被发现的，对这些天体的理论理解和预测还没有出现。在我的研究期间，我开发和利用了一个复杂的、最先进的星系形成模型，对UFD在暗物质晕中的形成和演化进行了极高分辨率的模拟。直到今天，这些极其微弱的星系的如此详细和高分辨率的模型都是不可能的。在我的研究中，我使用我的模拟详细探索UFD和它们的暗物质晕之间的联系。我将解决诸如UFD的暗物质含量是多少以及它们的暗物质晕有多大等问题？什么是最小的光环，主机UFD？UFD是宇宙大爆炸后形成的第一批星系之一。我跟随这些物体在它们的暗物质晕中的形成，探索它们不同的形成通道。此外，我还研究了这些第一批星系在宇宙非常年轻的时候是如何影响它们的环境的。目前已知的大多数UFD都位于我们附近，即我们自己的星系，银河系周围，并且是银河系的卫星。在接下来的几年里，预计将使用即将到来的望远镜（例如超大望远镜）发现更多这些极其微弱的物体。目前还不知道还有多少UFD等待发现。利用我的研究，我预测了银河系周围预计存在多少UFD以及它们是如何分布的。我的发现将指导未来几年寻找失踪的矮星系和UFD。总之，我在宇宙学背景下研究超微弱矮星系的形成和演化，以了解暗物质晕和暗端星系之间的联系，并为即将到来的望远镜提供预测（例如极大望远镜和詹姆斯韦伯太空望远镜），预计将在附近的宇宙中发现更多的这些星系，以及早期。

My research focuses on exploring one of the fundamental unknowns in physics and cosmology: mysterious "dark matter" which makes up 80% of the matter in the Universe. The nature of dark matter is not known but its evidence in galaxies and clusters of galaxies has been observed using its gravitational influence on the matter and light; e.g. affecting the motion of stars in galaxies.According to the current cosmological model, galaxies inhabit the centre of more extended dark matter halos. The dark matter halos of low mass galaxies (dwarf galaxies) and their fainter counterparts (ultra faint dwarfs or UFDs) are thought to be much more massive than the galaxies themselves. Dwarf galaxies and UFDs are therefore excellent laboratories to explore the properties of dark matter. Due to their low mass and faint nature, however, the study of these objects has been observationally and theoretically challenging. Most of the known UFDs have been discovered only in the very recent years, and theoretical understanding of, and predictions for, these objects are missing from the picture.During my fellowship, I develop and exploit extremely high resolution simulations of the formation and evolution of UFDs in their dark matter halos using a complex, state-of-the-art galaxy formation model. Such detailed and high resolution models of these extremely faint galaxies have not been possible up to this day.In my studies, I explore in detail the connection between UFDs and their dark matter halos using my simulations. I will address questions such as what is the dark matter content of UFD and how massive are their dark matter halos? What is the smallest halo that host UFDs? UFDs are amongst the first galaxies to form in the Universe after the Big Bang. I follow the formation of these objects in their dark matter halos and explore their different formation channels. Moreover, I study how these first galaxies affect their environment when the Universe was very young.Most of the currently known UFDs are located close to us, i.e. around our own galaxy, the Milky Way, and are satellites of the Milky Way. More of these extremely faint objects are expected to be discovered in the following years using up-coming telescopes, e.g. the Extremely Large Telescope. It is however not known how many more UFD are awaiting discovery. Using my research, I predict how many UFDs are expected to exist around the Milky Way and how they are distributed. My findings will guide the search for the missing dwarfs and UFDs in the up-coming years.In summary, I study the formation and evolution of ultra faint dwarf galaxies in a cosmological context in order to understand the connection between dark matter halos and galaxies at the faint end, and to provide predictions for the up-coming telescopes (e.g. the Extremely Large Telescope and the James Webb Space Telescope) which are expected to discover more of these galaxies in the nearby Universe, as well as early times.