Dynamics of Multiphase Carbon in the Turbulent Circumgalactic Medium

Abstract The circumgalactic medium (CGM) plays a crucial role in regulating material and energy exchange between galaxies and their environments. The best means of observing this medium is through absorption-line spectroscopy, but we have yet to develop a consistent physical model that fully explains the results. Here we investigate the impact of turbulence and nonequilibrium chemistry on the properties of the CGM, using three-dimensional hydrodynamic simulations that include the impact of an ionizing background. Increasing turbulence enhances small-scale density fluctuations, shifting the kinetic energy spectra from Kolmogorov to Burgers scaling. This is indicative of shock-dominated dissipation, which plays a critical role in driving carbon ionization and shaping the multiphase structure of the medium. At the same time, the presence of background radiation significantly alters the ionization balance, increasing the prevalence of C ii and C iv . Thus, turbulence and the background radiation have complementary roles: turbulence governs the spatial distribution and facilitates the formation of ionized species, whereas the background radiation modifies the overall ionization equilibrium, setting the observed distribution of multiphase carbon.