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

环星系介质(CGM)是星系外的气库，它调节了星系和星际介质之间的相互作用，宇宙中的大部分重子物质都居住在星际介质中。它的结构和运动学影响恒星的形成和星系的生长；但对CGM的了解在观测和理论上都是有限的。该项目的提出者将结合对CGM的模拟和观测，以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，用于在自适应网格宇宙模拟中选择性地提高分辨率，并使用“活动粒子”来模拟恒星分量，包括来自超新星爆炸的动量反馈。他们将使用这种方法在宇宙学的背景下研究晕气体的动态演化，因为它被整合到星系盘中。在第二部分中，该团队将设计出描述气体成分在物理和运动空间中的分布的量化措施。他们将使用这些测量方法将高分辨率模拟与多波长观测进行比较，测试气体吸积理论，并确定银河系光晕中是否存在大型、有组织的流动。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.