The Milky Way and its neighbours in the era of large surveys

最近绘制的银河系和仙女座星系外围的恒星分布图，从视觉上惊人地展示了离中心很远的星系的巨大复杂性。他们展示了矮星系，以及恒星流和其他弥散结构，作为同一个“星系生态系统”的一部分，据此星系之间的相互作用和较小星系合并为较大星系似乎代表了这些物体生命周期的一部分。新的和即将到来的设施——最直接的是盖亚，以及LSST和TMT——为更好地理解这个生态系统、矮星系在其中的作用以及它与宇宙学范式的一致性（或其他）提供了显著的定性进展机会。我研究的一个核心目标是利用盖亚带来的机会，并通过一个以研究生培训为中心的研究项目，为即将到来的科学、技术和数据机会做好准备。具体来说，我的学生将使用大型调查数据集，我是PI，这些数据集是专门针对最近星系的具体研究而定制的，否则国际社会就无法解决这些问题。我的研究项目涵盖了恒星天体物理学、星系演化和宇宙学。众所周知，宇宙的大尺度结构被流行的宇宙学范式很好地描述了，它表明宇宙中的质量是“黑暗的”（即，它不发射电磁辐射）。然而，我们通过暗物质对发光物质的引力影响推断出它的存在，所有星系都被认为是在被称为“光晕”的暗物质集中区域形成的。现在研究人员的责任是在较小的空间尺度上测试这一范式，而这一理论最初并不是针对较小的空间尺度开发的。这里有一些有充分根据的、可测试的预测，但从星系形成的复杂物理中解开这些预测在观测上是非常困难的。离我们最近的星系为许多相关的观测提供了最好的机会。例如，星系晕本质上是非常微弱的，因为尽管它们是星系大部分质量的家园，但我们希望能够追踪潜在暗物质的恒星很少。此外，只有在邻近的宇宙中，我们才能接触到最小的（“矮”）星系，这些星系为宇宙学范式提供了一些最重大的挑战，并且似乎是存在的最暗物质主导的系统。我领导了几个项目，旨在提供关于矮星系和星系晕特性的基本数据。我的整体研究计划以研究生培训为中心，并利用这些具有国际竞争力的观测数据集和设施的高水平访问来推进这一蓬勃发展的领域。

Recent maps of the distribution of stars in the outskirts of the Milky Way and Andromeda galaxies are a startling visual demonstration of the immense complexity of galaxies at large distances from the centre. They show dwarf galaxies, as well as stellar streams and other diffuse structures, as part of the same ``galactic ecosystem'', whereby interactions between galaxies and the merging of smaller galaxies into larger galaxies appear to represent part of the life-cycle of these objects. New and upcoming facilities - most immediately Gaia, as well as LSST and TMT - provide remarkable opportunities for qualitative progress in better understanding this ecosystem, the role of dwarf galaxies within it, and its consistency (or otherwise) with the cosmological paradigm. A core goal of my research is to exploit opportunites presented by Gaia, and to prepare for these upcoming scientific, technological and data opportunities through a research program centered around graduate student training. Specifically, my students will use large survey datasets for which I am PI, and that are uniquely taylored to specific studies of the nearest galaxies that cannot otherwise be addressed by the international community. ***My research program straddles aspects of stellar astrophysics, galaxy evolution, and cosmology. It is well established that the large scale structure of the Universe is well described by the prevailing cosmological paradigm, and it indicates that mass in the Universe is "dark" (i.e., it does not emit electromagnetic radiation). We infer its presence, however, by its gravitational influence on luminous matter, and all galaxies are expected to form within dark matter concentrations called "halos". The onus is now on researchers to test this paradigm on smaller spatial scales for which the theory was not originally developed. Here, there are well-founded, testable, predictions, but unravelling these from the complex physics of galaxy formation is observationally very difficult. The nearest galaxies offer the best opportunities for many of the relevant observations. For example, galaxy halos are intrinsically very faint, since despite being home to most of the mass of the galaxy they have very few stars with which we can hope to trace the underlying dark matter. Further, it is only for the nearby Universe that we can access the smallest ("dwarf") galaxies that provide some of the most significant challenges for the cosmological paradigm, and which appear to be the most dark-matter dominated systems that exist. I lead several programs that are aimed at providing essential data on the properties of dwarf galaxies and on the properties of galaxy halos. My overall research program is centred around graduate student training and utilizes high level access to these internationally competitive observational datasets and facilities to advance this burgeouning field.