Origin, Evolution, and Implications of Wavelike Motions in the Stellar Disk of the Milky Way

测量银河系中恒星位置和速度的天文调查使我们能够了解银河系的动力学及其暗物质晕的结构。我的研究小组使用理论，模拟和数据分析的组合来探索和利用这些调查。从2012年开始，我们的重点一直放在一个假设上，即银河系的恒星盘表现出垂直的波状运动，即垂直于其中间面的运动。这项工作的动力是我和我的合作者发现了恒星数量的不对称性，这与附近恒星的平面和垂直运动有关。不久之后，其他研究人员通过不同的调查发现了类似的特征。此外，在更远的银河系圆盘上还发现了波纹或波纹。一种可能性是，这些特征是由经过的卫星星系的引力场引起的。我的研究计划的目标是通过理论分析和模拟来寻找扰动盘的新证据，并发展对垂直波的理解。此外，我的小组将探索盘不平衡对关键项目的影响，如确定银河系引力势和太阳系附近暗物质的数量。简而言之，这项我们称之为“星系地震学”的努力，旨在通过研究星系盘中的波状运动来了解银河系的结构及其环境。上述发现是通过对数十万颗恒星的天文测量得出的。银河动力学领域现在专注于盖亚，这是一个欧洲空间天文台，将测量超过10亿颗恒星的6D相位空间坐标，从而将相位空间测量的恒星数量增加3-4个数量级。盖亚的第二次数据发布提供了700万颗恒星的6D测量，已经产生了有趣的结果，比如太阳附近奇怪的相空间螺旋。像这样的相空间结构提供了一个潜在的银河系潜力的强大探测。我研究的一个重点是将数据科学方法应用于盖亚数据的分析，以努力揭示恒星分布的其他特征。这些方法包括计算机视觉领域的核密度估计和脊查找算法。我的研究项目也使用星系的n体模拟来验证我们的假设。“观察”模拟快照以生成可与实际数据进行比较的模拟数据目录。模拟也为检验我们对星系动力学的理解提供了机会。研究生和本科生将参与我的研究计划的各个方面，并将在理论天体物理学、计算方法和数据科学方面获得宝贵的培训。

Astronomical surveys that measure the positions and velocities of stars in the Milky Way allow us to learn about the dynamics of the Galaxy and the structure of its dark matter halo. My research group uses a combination of theory, simulations, and data analysis to explore and exploit these surveys. Beginning in 2012, our focus has been on the hypothesis that the stellar disk of the Milky Way exhibits vertical wavelike motions, that is, motions normal to its midplane. The impetus for this work was the discovery by me and my collaborators of asymmetries in stellar number counts with respect to the midplane and vertical bulk motions of nearby stars. Soon after, similar features were found by other researchers using different surveys. In addition, ripples or corrugations were discovered in the further out in the Milky Way's disk. One possibility is that these features were caused by the gravitational field of a passing satellite galaxy. The goal of my research program is to search for new evidence of a perturbed disk and develop an understanding of vertical waves through theoretical analysis and simulations. In addition, my group will explore the implications of disk disequilibrium for key projects such as the determination of the Galactic gravitational potential and the amount of dark matter in the Solar Neighbourhood. In short, this endeavour, which we have dubbed Galactoseismology, aims to learn about the structure of the Galaxy and its environment by studying wavelike motions in the disk. The discoveries described above were made with surveys that included astrometric measurements of hundreds of thousands of stars. The field of Galactic Dynamics is now focused on Gaia, a European Space Observatory that will measure 6D phase space coordinates for over one billion stars and thereby increase the number of stars with phase space measurements by a staggering 3-4 orders of magnitude. Already, Gaia's 2nd Data Release, which provides 6D measurements for 7M stars, has produced intriguing results, such as curious phase space spirals near the Sun. Phase space structures such as these provide a potentially powerful probe of the Galactic potential. One thrust of my research will be to apply data science methods to the analysis of the Gaia data in an effort to uncover other features in the distribution of stars. These methods include kernel density estimation and ridge finding algorithms from the field of computer vision. My research program also uses N-body simulations of galaxies to test our hypotheses. The simulation snapshots are "observed" to generate mock data catalogs that can be compared with actual data. Simulations also provide an opportunity to test our understanding of galactic dynamics. Graduate and undergraduate HQP will be involved in all aspects of my research program and will gain valuable training in theoretical astrophysics, computational methods, and data science.