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，宇宙中只有不到5%的物质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”和“暗能量”组成的，暗物质具有物质的引力性质，但几乎不与光相互作用(25%)，还有“暗能量”，它的作用是排斥引力。天体物理学家将这个模型进一步发展成一个暗物质以慢速粒子的形式存在，暗能量与爱因斯坦最先提出的宇宙常数有关的模型。该模型在解释许多观测到的宇宙特征方面取得了显著的成功。尽管如此，该模型与我们所在的银河系及其邻近星系的观测属性之间仍然存在不匹配。这项由该职业奖支持的工作将利用双子座天文台来解决这些根本问题，并对暗物质的性质提供新的限制。美国国家科学基金会是双子座天文台的创始合作伙伴。国际和平研究所，Nitya Kallivayalil博士，还将启动并领导与斯佩尔曼学院的重大合作，斯佩尔曼学院是美国历史上最古老的黑人女子学院，为来自代表不足的群体培养未来的STEM领导人创造了一个渠道。国际和平研究所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，来测量银河系引力势的示踪器的6维相空间。这需要准确的自身运动，以及广泛分布在整个光晕中的场星和卫星的径向速度。PI将明确限制银河系的暗晕形状、方向、径向轮廓和总质量；确定其卫星星系的坠落时间；并约束矮小星系的中心密度分布，以评估它们是否具有尖状或核状轮廓。此外，PI与斯佩尔曼学院的合作将涉及面向斯佩尔曼学生的本科生研究体验REU计划，以及该学院的课程开发。

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.