CAREER: The Dynamics of the Milky Way's Local Group Substructure as the Key to Understanding Dark Matter and Galaxy Formation

有压倒性的天体物理学证据表明，只有不到5%的宇宙是由普通物质或重子物质组成的。宇宙的其余部分似乎是由“暗物质”组成的，它具有物质的引力特性，但几乎不与光相互作用（25%），以及“暗能量”，它的作用是排斥引力。天体物理学家进一步发展了这个模型，其中暗物质以缓慢移动的粒子的形式存在，暗能量与爱因斯坦首次引入的“宇宙常数”有关。该模型在解释宇宙的许多观测特征方面取得了显著的成功。尽管如此，该模型与我们银河系及其邻居的观测特性之间仍然存在不匹配。这项CAREER奖支持的工作将使用Gemini天文台，NSF是该天文台的创始合作伙伴，以解决这些基本问题，并为暗物质的性质提供新的限制。PI Nitya Kallivayalil博士还将发起并领导与美国历史最悠久的黑人女子学院Spelman College的重大合作，为来自代表性不足的群体的未来STEM领导者创建一个管道。PI计划的具体目标是使用双子座天文台采用的世界领先的自适应光学技术，以及其创新的大型和长期观测计划，测量银河系引力势示踪物的6维相空间。这需要精确的自行，以及广泛分布在整个晕中的场星和卫星的径向速度。PI将明确限制暗晕的形状，方向，径向轮廓和银河系的总质量;确定其卫星星系的坠落时间;并限制矮星系的中心密度分布，以评估它们是否具有尖点或核心状轮廓。此外，PI与Spelman学院的合作伙伴关系将涉及Spelman学生的本科生REU计划的研究经验，以及学院的课程开发。

There is overwhelming astrophysical evidence that less than 5 percent of the universe is made from ordinary - or baryonic - matter. The rest of the cosmos appears to be constituted from "dark matter," which has the gravitational properties of matter but which hardly interacts with light (25 percent), together with "dark energy," which acts to repel the force of gravity. Astrophysicists have further developed this model into one in which dark matter takes the form of slow-moving particles, and dark energy is associated with a "cosmological constant" first introduced by Einstein. The model has had remarkable successes in explaining many of the observed characteristics of the universe. Nonetheless, there remain mismatches between the model and the observed properties of our own Milky Way galaxy and its neighbors. The work supported by this CAREER award will use the Gemini Observatory, of which the NSF is a founding partner, to tackle these fundamental problems and provide new constraints on the nature of dark matter. The PI, Dr. Nitya Kallivayalil, will also launch and lead a major collaboration with Spelman College, America's oldest historically Black college for women to create a pipeline for training future STEM leaders from under-represented groups.The specific goals of the PI's program are to use the world-leading adaptive optics technologies employed by the Gemini Observatory, together with its innovative large and long observing programs, to measure the 6-dimensional phase space of tracers of the Milky Way's gravitational potential. This requires accurate proper motions, in addition to radial velocities for field stars and satellites widely distributed throughout the halo. The PI will definitively constrain the dark-halo shape, orientation, radial profile and total mass of the Milky Way; determine the infall times of its satellite galaxies; and constrain the central density distributions of dwarf galaxies to assess whether they have cusp- or core-like profiles. Furthermore, the PI's partnership with Spelman College will involve a Research Experiences for Undergraduates REU program for Spelman students, as well as curriculum development at the college.