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

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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.