Directly Testing the Presence of Large-Scale Multiphase Flows in the Galactic Halo

环星系介质（CGM）是星系外的气体储层，是星系与星系间介质相互作用的中介，宇宙中大部分重子物质都存在于星系间介质中。它的结构和运动学影响恒星的形成和星系的成长；但是对CGM的认识在观测和理论上都是有限的。这个项目的提议者将结合CGM的模拟和观测来约束星系形成的理论。在该项目的第一部分，该团队将开发新的计算方案，以选择性地提高自适应网格宇宙学模拟的分辨率，并使用“活性粒子”来模拟恒星成分，包括超新星爆炸的动量反馈。他们将用这种方法在宇宙学的背景下研究光环气体的动态演化，因为它被整合到一个星系盘中。在第二部分中，该团队将设计定量测量，描述气体成分在物理和运动空间中的分布。他们将使用这些测量来比较高分辨率模拟与多波长观测，测试气体吸积理论，并确定在银河系的光晕中是否存在大型的、有组织的气流。该项目将支持一名研究生的工作。模拟的三维可视化将在纽约市和美国自然历史博物馆的天文推广活动中制作和展示；团队成员将参加哥伦比亚大学正在进行的一个项目，将研究生和博士后带到纽约的中学。

The circumgalactic medium (CGM), the gas reservoir outside galaxies, mediates the interaction between galaxies and the intergalactic medium, where most of the baryonic matter in the universe resides. Its structure and kinematics influence star formation and the growth of galaxies; but knowledge of the CGM remains limited both observationally and theoretically. The proposers of this project will combine simulations and observations of the CGM to constrain theories of galaxy formation. In the first part of the project, the team will develop new computational schemes for selectively improving resolution in adaptive mesh cosmological simulations and for using "active particles" to model the stellar component including momentum feedback from supernova explosions. They will use this approach to examine the dynamic evolution of halo gas in a cosmological context as it is integrated into a galactic disk. In the second part, the team will devise quantitative measures describing the distributions of gas components in physical and kinematic space. They will use these measures to compare high resolution simulations with multi-wavelength observations, test theories of gas accretion, and determine whether large, organized flows are present in the halo of the Milky Way. The project will support the work of a graduate student. Three-dimensional visualizations of the simulations will be produced and displayed at astronomy outreach events in New York City and at the American Museum of Natural History; and team members will participate in an ongoing program at Columbia University to bring graduate students and postdocs to New York middle schools.