Merger-Driven Turbulence and Coherent Transport in the Intracluster Medium

Abstract

The distribution of metals and temperature in the intracluster medium (ICM) provides key insights into galaxy cluster evolution, revealing information about chemical enrichment and heating and cooling processes, respectively. To access this information, it is crucial to understand the transport processes in the ICM. Here, we systematically study the transport mechanisms in the ICM with tracer particle resimulations of the Omega500 cosmological hydrosimulation, using a sample of four galaxy clusters of comparable masses but different mass assembly histories. Through the analysis of particle pair dispersion statistics, we find a time-dependent scaling index linked to the cluster's dynamical state. It reaches or exceeds Richardson scaling briefly during major mergers but remains much lower in relaxed clusters. We identify a coherent transport mode during major mergers that causes directional flow in the ICM. Although coherent transport can move particles to outer regions, the particles transported to the cluster outskirts compose only a small fraction of the density there; thus the anisotropy it creates in the overall density distribution is limited. Moreover, strong turbulence generated by mergers quickly disperses these particles, further limiting this effect. We also provide useful statistics on the radial evolution of the ICM and the fraction of particles that ever reached the inner regions as a function of radius. Our results show that major mergers primarily drive particle transport, linking ICM transport to merger-driven dynamics, and highlighting the interplay between coherent and turbulent transport.