Measuring the hot ICM velocity structure function using XMM-Newton observations

TL;DR

This study measures the velocity structure function of the hot intracluster medium using XMM-Newton data, revealing turbulence scales and dynamics in galaxy clusters with different activity levels.

Contribution

First direct measurement of the ICM velocity structure function using X-ray data, providing insights into turbulence and heating processes in galaxy clusters.

Findings

Turbulence driving scale of 10-20 kpc in Virgo cluster.

Absence of strong AGN interaction in Ophiuchus reflected in VSF.

Dissipation time exceeds jet activity cycle, implying other heating mechanisms.

Abstract

It has been shown that the gas velocities within the intracluster medium (ICM) can be measured by applying novel XMM-Newton EPIC-pn energy scale calibration, which uses instrumental Cu Ka as reference for the line emission. Using this technique, we have measured the velocity distribution of the ICM for clusters involving AGN feedback and sloshing of the plasma within the gravitational well (Virgo and Centaurus) and a relaxed one (Ophiuchus). We present a detailed study of the kinematics of the hot ICM for these systems. First, we compute the velocity probability distribution functions (PDFs) from the velocity maps. We find that for all sources the PDF follows a normal distribution, with a hint for a multimodal distribution in the case of Ophiuchus. Then, we compute the velocity structure function (VSF) for all sources in order to study the variation with scale as well as the nature of turbulence in the ICM. We measure a turbulence driving scale of 10-20 kpc for the Virgo cluster, while the Ophiuchus cluster VSF reflects the absence of strong interaction between the ICM and a powerful Active Galactic Nucleus (AGN) at such spatial scales. For the former, we compute a dissipation time larger than the jet activity cycle, thus indicating that a more efficient heating process than turbulence is required to reach equilibrium. This is the first time that the VSF of the hot ICM has been computed using direct velocity measurements from X-ray astronomical observations.