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AR 15800 (Archival Research)

Sun Jul 14 19:14:21 GMT 2024

Principal Investigator: Cameron Hummels
PI Institution: California Institute of Technology
Investigators (xml)

Title: A subgrid model for simulating the unresolved microphysics in the circumgalactic medium
Cycle: 27

Abstract
The majority of galactic baryons reside outside of the galactic disk in the diffuse gas known as the circumgalactic medium (CGM). While state-of-the art simulations excel at reproducing properties of the galactic disk, they struggle to reproduce the observational characteristics of the CGM, most notably the observed column densities and kinematics of cool (T ~ 10^4 K) gas. The survival of cool gas in the CGM is governed by physical processes that are unresolved in existing simulations. Recent work has demonstrated how increasing halo resolution leads to qualitatively different abundances and behavior of the CGM, but this behavior is not predicted to converge until sub-parsec scales are reached. Even with adaptive mesh refinement, fully resolving the CGM at these scales requires computational resources not expected to exist for several decades. We propose developing the first subgrid model to track the unresolved cool phase of the CGM in cosmological hydrodynamics simulations of galaxy evolution. The unique strength of this model is that it requires no tuning, as it derives from robust representations of the underlying small-scale physics. Our model and its implementation in two popular astrophysical hydrodynamics codes, Enzo and Gizmo, will be released publicly to help jump start use of this transformational method by the community. Lastly, the model will be employed on large-scale cosmological zoom simulations to address key science drivers of how the cool gas of the CGM behaves, where metals go, and how galaxies quench.