Structure of the Circumgalactic Medium in High-Resolution Cosmological Simulations

ABSTRACT: The circumgalactic medium (CGM) surrounding galaxies regulates gas flows between galaxies and the broader Universe to affect how galaxies grow and evolve. High-resolution simulations of the CGM reveal detailed structure, kinematics, and time-dependence in the gas that are frequently overlooked by analytic, idealized, or low-resolution models of galaxy halos. I will show that non-thermal gas motions, such as turbulence and the bulk flows of inflowing filaments or outflowing galactic winds, are critically important to determining the overall structure, support against gravity, and even temperature of the CGM gas in the Figuring Out Gas & Galaxies In Enzo (FOGGIE) high-resolution cosmological zoom-in simulations. In addition, stochastic events in a galaxy’s evolution, such as strong bursts of star formation feedback triggered by mergers, heat and stir the CGM gas into a non-equilibrium state that persists for billions of years. Altogether, I will show how the high-resolution FOGGIE CGM simulations indicate that galaxies evolve subject to small-scale and non-equilibrium processes, which can be described with classical global equilibrium models of galaxy evolution only when smoothed over large scales in space and time.