Speaker
Description
Most of a galaxy's gas resides in its halo's atmosphere, known as the circumgalactic medium (CGM). Like our own atmosphere, the CGM consists of a hotter, volume-filling component and cooler clouds that can 'rain' onto the galaxy's disc and fuel the formation of new stars. However, simulating the cooler clouds and the entire atmosphere simultaneously poses significant computational challenges, since the short cooling length of the densest clouds demands high spatial resolution.
To address this challenge, we conduct a suite of high-resolution magnetohydrodynamic simulations, modeling the CGM as turbulent boxes spanning 1-10 kpc, where the smaller boxes resolve the cooling length better. By systematically varying the box size, we explore two distinct scenarios: constant turbulent heating rate (which maintains the energy cascade) and fixed cooling-to-mixing time ratio, a critical parameter governing cold cloud survival. Our analysis focuses on the survival of cold clouds and their kinematics, distinguishing between internal motions and group velocities within the hot medium and comparing them against the kinematics of the hot phase. We validate our findings against observational line width-size relations for cold clouds and generate synthetic column densities for key ions (MgII, SiIV, OVI), enabling direct comparison with quasar absorption line data. Additionally, we explore alternative turbulence diagnostics, including velocity and density power spectra, comparing their characteristics in single-phase and multiphase turbulence regimes. This analysis has important implications for understanding the scattering of Fast Radio Burst signals in the multiphase CGM, where AU-scale density fluctuations within the cold clouds could play an important role.
