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

银河系恒星盘中波状运动的起源、演化和影响

• 批准号: RGPIN-2019-04691
• 负责人: Widrow, Lawrence
• 金额: $ 2.48万
• 依托单位: Queen's University
• 依托单位国家: 加拿大
• 项目类别: Discovery Grants Program - Individual
• 财政年份: 2021
• 资助国家: 加拿大
• 起止时间: 2021-01-01 至 2022-12-31
• 项目状态: 已结题
• 来源: https://www.nserc-crsng.gc.ca/ase-oro/Details-Detailles_eng.asp?id=737791
• 关键词: Origin; Evolution; Implications; Wavelike; Motions

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.

测量银河系中恒星的位置和速度的天文测量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、模拟和数据分析相结合的方法来探索和利用这些调查。从2012年开始，我们的重点一直放在银河系恒星盘呈现垂直波状运动的假设上，即垂直于其中面的运动。这项工作的推动力是我和我的合作者发现了恒星数计数相对于附近恒星的中面和垂直整体运动的不对称性。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，在银河系盘面更远的地方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造成的。我的研究计划的目标是寻找扰动圆盘的新证据，并通过理论分析和模拟发展对垂直波的理解。此外，我的团队将探索盘不平衡对关键项目的影响，例如确定银河系引力势和太阳近邻中暗物质的数量。简而言之，这项我们称之为银河地震学的努力，旨在通过研究盘中的波动运动来了解银河系的结构和环境。上面描述的这些发现是通过对数十万颗恒星进行天体测量的调查得出的。银河动力学的领域现在集中在GAIA上，这是一个欧洲空间天文台，将测量超过10亿颗恒星的6D相空间坐标，从而使相空间测量的恒星数量惊人地增加3-4个数量级。盖亚第二次发布的数据提供了对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强大的银河系势能探测器。我的研究重点之一将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。这些方法包括来自计算机视觉领域的核密度估计和脊线寻找算法。我的研究项目还使用星系的N体模拟来验证我们的假设。模拟快照被“观察”以生成可与实际数据进行比较的模拟数据目录。模拟也提供了一个机会来测试我们对星系动力学的理解。研究生和本科生HQP将参与我研究计划的所有方面，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。