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

点击翻译按钮获取中文摘要

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.