Monday

Turbulence plays an important role in the kinematics and thermodynamics of the gas in the intracluster medium (ICM). In cluster outskirts, it provides non-thermal pressure support to the ICM gas and is important in estimating cluster masses. In the central regions of cool core clusters, turbulence driven by Active Galactic Nuclei (AGN) jets can heat the ICM via viscous dissipation and prevent runaway cooling flows.

However, it has been difficult to directly measure the velocities of the ICM gas, after the sad end of the Hitomi telescope. Instead, we rely on indirect methods such as measuring X-ray surface brightness (SB) fluctuations, thermal Sunyaev-Zeldovich (tSZ) effect to obtain estimates of turbulent gas velocities.

In our study, we have checked for the impact of the strength of background stratification on the different statistical properties of ICM gas, like density and pressure fluctuations, which are used for estimating turbulence through the SB and SZ methods, respectively.

We perform high-resolution hydrodynamical simulations of turbulence with different levels of stratification. For the purpose of diagnosis and characterisation of turbulent velocities in the ICM, we derive scaling relations between the density and pressure fluctuations, rms Mach number, and the strength of background stratification (Richardson number/ Froude number). These scaling relations can be used to calculate turbulent velocities accurately from both X-ray brightness images and thermal SZ-effect measurements.