Collaborative Research: Stellar Clouds as New Probes of the Milky Way's Accretion History and Mass Distribution

围绕星系的暗物质晕的径向轮廓、形状、范围和方向是什么？这一根本问题在星系外围尤其难以解决，因为那里几乎没有可见的示踪物。也许最有希望的方法是使用摧毁卫星星系的恒星碎片，而最有希望尝试这种方法的地方是银河系--宇宙中唯一一个可以直接探测到光晕的三维结构(而不是二维投影)的星系。这个奖项将支持一种观测和理论相结合的方法，为吸积的光晕亚结构提供一个新的、强大的视角，特别是研究较少的星云。观测计划的重点是获取已知恒星云中恒星的径向速度，并在碎片结构之间建立联系-从太阳附近到外银河系，从银河系的一边到另一边。这样的连接将产生第一张银河系尺度上这些恒星碎片结构的全面地图。用一套系统的模拟来解释这些地图，将填补我们对银河系吸积史和物质分布的缺失知识。该奖项将支持一名少数族裔学生通过参加哥伦比亚大学的“博士之桥”项目，在从本科生过渡到研究生的过程中进行培训。这也将使私人投资者能够积极参与学生、业余天文学家和公众对我们的银河系历史的了解。

What are the radial profiles, shapes, extents and orientations of the dark matter halos that surround galaxies? This fundamental question is particularly difficult to address in the outskirts of galaxies where there are few visible tracers. Perhaps the most promising approach is to use stellar debris from the destruction of satellite galaxies, and the most promising place to try this approach is the Milky Way - the one galaxy in the Universe where a halo's 3-dimensional structure (rather than a 2-dimensional projection) can be directly probed.This award will support a combined observational and theoretical approach to providing a new and powerful perspective on accreted halo substructures, and, in particular, poorly-studied stellar clouds. The observational program focuses on obtaining radial velocities for stars in known stellar clouds, and making connections between debris structures - from the Solar vicinity to the outer Galaxy, and from one side of the Galaxy to another. Such connections will yield the first comprehensive maps of these stellar debris structures on Galactic scales. Interpreting these maps with a systematic suite of simulations will fill in our missing knowledge of the Galaxy's accretion history and matter distribution.This award will support the training of one minority student in their transition from undergraduate to graduate school through participation in Columbia's "Bridge to the PhD" program. It will also enable the PIs to actively engage students, amateur astronomers and the general public in building an understanding of the history of our home galaxy.