Turbulence and Vorticity in Galaxy Clusters Generated by Structure Formation

Abstract

Turbulence is a key ingredient for the evolution of the intracluster medium, whose properties can be predicted with high resolution numerical simulations. We present initial results on the generation of solenoidal and compressive turbulence in the intracluster medium during the formation of a small-size cluster using highly resolved, non-radiative cosmological simulations, with a refined monitoring in time. In this first of a series of papers, we closely look at one simulated cluster whose formation was distinguished by a merger around $z\sim 0.3$. We separate laminar gas motions, turbulence and shocks with dedicated filtering strategies and distinguish the solenoidal and compressive components of the gas flows using Hodge-Helmholtz decomposition. Solenoidal turbulence dominates the dissipation of turbulent motions ($\sim 95\%$) in the central cluster volume at all epochs. The dissipation via compressive modes is found to be more important ($\sim 30\%$ of the total) only at large radii ($\ge 0.5r_{\mathrm{vir}}$) and close to merger events. We show that enstrophy (vorticity squared) is good proxy of solenoidal turbulence. All terms ruling the evolution of enstrophy (i.e. baroclinic, compressive, stretching and advective terms) are found to be significant, but in amounts that vary with time and location. Two important trends for the growth of enstrophy in our simulation are identified: first, enstrophy is continuously accreted into the cluster from the outside, and most of that accreted enstrophy is generated near the outer accretion shocks by baroclinic and compressive processes. Second, in the cluster interior vortex stretching is dominant, although the other terms also contribute substantially.

21 pages, 21 figure. MNRAS accepted, in press

References in corpus (18)

• The Quiescent Intracluster Medium in the Core of the Perseus Cluster
• Turbulence and Magnetic Fields in the Large Scale Structure of the Universe
• Compressible Turbulence in Galaxy Clusters: Physics and Stochastic Particle Re-acceleration
• Turbulent Heating in Galaxy Clusters Brightest in X-rays
• Hydrodynamic Simulation of Non-thermal Pressure Profiles of Galaxy Clusters
• Shock Waves in Eulerian Cosmological Simulations: Main Properties and Acceleration of Cosmic Rays
• Cosmological Shocks in Adaptive Mesh Refinement Simulations and the Acceleration of Cosmic Rays
• Resolving the Formation of Protogalaxies. I. Virialization
• Comparing Numerical Methods for Isothermal Magnetized Supersonic Turbulence
• On the amplification of magnetic fields in cosmic filaments and galaxy clusters
• The relation between gas density and velocity power spectra in galaxy clusters: high-resolution hydrodynamic simulations and the role of conduction
• Chemical Enrichment RGS cluster sample (CHEERS): Constraints on turbulence
• The Matryoshka Run (II): Time Dependent Turbulence Statistics, Stochastic Particle Acceleration and Microphysics Impact in a Massive Galaxy Cluster
• Turbulent Velocity Fields in SPH--simulated Galaxy Clusters
• Magnetic field amplification by shocks in galaxy clusters: application to radio relics
• Vorticity of IGM Velocity Field on Large Scales
• On the Cluster Physics of Sunyaev-Zel'dovich and X-ray Surveys IV: Characterizing Density and Pressure Clumping due to Infalling Substructures
• Influence of adaptive mesh refinement and the hydro solver on shear-induced mass stripping in a minor-merger scenario

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