Simulating Galactic Winds on Supercomputers Using Cholla

Evan Schneider (University of Arizona)

September 19, 2016

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Abstract: Galactic winds are a ubiquitous feature of rapidly star-forming galaxies. Observations have revealed these outflows to be complex, multiphase phenomena, with gas at a large range of densities and temperatures traveling at speeds from a few tens to more than 1000 kilometers per second. Describing how these outflows originate, evolve, and affect the circumgalactic medium and gas supply of galaxies is an important challenge for theories of galaxy evolution. In this talk, I will discuss how we are using a new hydrodynamics code, Cholla, to improve our understanding of galactic winds. Cholla is a massively parallel, GPU-based code that I wrote to take advantage of the newest generation of supercomputers. With Cholla, we can perform large, three-dimensional simulations of multiphase outflows, allowing us to track the coupling of mass and momentum between gas phases across hundreds of parsecs at sub-parsec resolution. The results of our recent simulations demonstrate that the evolution of cool gas in galactic winds is highly dependent on the initial structure of embedded clouds. In particular, we find that turbulent density structures lead to more efficient mass transfer from cool to hot phases of the wind. I will discuss the implications of our results both for the incorporation of winds into cosmological simulations, and for interpretations of observed multiphase winds and the circumgalactic medium of nearby galaxies.