Dynamics of Multiphase Carbon in the Turbulent Circumgalactic Medium

TL;DR

This study uses hydrodynamic simulations to explore how turbulence and background radiation influence the multiphase carbon structure in the turbulent circumgalactic medium, providing insights into observed absorption-line spectra.

Contribution

It introduces a comprehensive model combining turbulence and non-equilibrium chemistry to explain the ionization and structure of the CGM.

Findings

Turbulence shifts energy spectra from Kolmogorov to Burgers scaling.

Background radiation increases CII and CIV ionization.

Turbulence and radiation jointly shape the multiphase carbon distribution.

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 these results. Here we investigate the impact of turbulence and non-equilibrium 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\textsc{ii} and C\textsc{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.