Shock waves in Eulerian cosmological simulations: main properties and acceleration of cosmic rays

By Franco Vazza, Gianfranco Brunetti, Claudio Gheller. 2008

151 citations recorded by the source corpus.

Large-scale shocks are responsible for the heating of the intracluster medium and can be important sources of cosmic rays (CRs) in the Universe. However, the occurrence and properties of these shocks are still poorly constrained from both a theoretical and an observational side. In this work we analyse the properties of large-scale shocks in a (103 Mpc h−1)3 cosmological volume simulated with the public 1.0.1 release of the enzo code. Different methods to identify and characterize shocks in post-processing are discussed together with their uncertainties. Re-ionization affects the properties of shocks in simulations, and we propose a fitting procedure to model accurately the effect of re-ionization in non-radiative simulations, with a post-processing procedure. We investigate the properties of shocks in our simulations by means of a procedure which uses jumps in the velocity variables across the cells in the simulations and this allows us to have a viable description of shocks also in relatively underdense cosmic regions. In particular we derive the distributions of the number of shocks and of the energy dissipated at these shocks as a function of their Mach number, and discuss the evolution of these distributions with cosmological time and across different cosmic environments (clusters, outskirts, filaments, voids). In line with previous numerical studies relatively weak shocks are found to dominate the process of energy dissipation in the simulated cosmic volume, although we find a larger ratio between weak and strong shocks with respect to previous studies. The bulk of energy is dissipated at shocks with Mach number M≈ 2 and the fraction of strong shocks decreases with increasing the density of the cosmic environments, in agreement with semi-analytical studies in the case of galaxy clusters. We estimate the rate of injection of CR at large-scale shocks by adopting injection efficiencies taken from previous numerical calculations. The bulk of the energy is dissipated in galaxy clusters and in filaments and the flux dissipated in the form of CR within the whole simulated volume at the present epoch is ≈0.2 of the thermal energy dissipated at shocks; this fraction is smaller within galaxy clusters. Finally, we discuss the properties of shocks in galaxy clusters in relation with their dynamical state. In these regions the bulk of the energy is dissipated at weak shocks, with Mach number ≈1.5, although slightly stronger shocks are found in the external regions of merging clusters.

Subfields: Astronomy and Astrophysics, Nuclear and High Energy Physics

View Paper: https://www.semanticscholar.org/paper/ce41fd82f5c89858e3f40e5a170bc702e0c1af37

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Citations in the corpus

A low-frequency radio halo associated with a cluster of galaxies (2008, background): “In order to derive a solid and conservative upper limit we follow [ 7 ,15] . We injected fake halos”
Turbulent Motions and Shocks Waves in Galaxy Clusters simulated with AMR (2009, methodology): “In the case that AMR is forced to increase the spatial resolution also around shocks, as our simulations with the novel AMR criterion, the Vazza et al.(2009) shock detecting scheme can be straightforwardly applied to simulated data at the highest available AMR level (therefore excluding our d128…”
DIFFUSIVE SHOCK ACCELERATION SIMULATIONS OF RADIO RELICS (2012, background): “…in filaments and outside cluster virial radii, shocks produced by mergers and flow motions in hotter ICMs are relatively weak with Mach number M . a few (Ryu et al. 2003; Pfrommer et al. 2006; Kang et al. 2007; Skillman et al. 2008; Hoeft et al. 2008; Vazza et al. 2009; Brüggen et al. 2011).”
Massive and refined - II. The statistical properties of turbulent motions in massive galaxy clusters with high spatial resolution (2010, methodology): “In the second method, following previous works on the same topic (e.g. Dolag et al. 2005; Vazza et al. 2006; Vazza et al. 2009; Vazza, Gheller & Brunetti 2010) we mapped the 3–”
ON THE CLUSTER PHYSICS OF SUNYAEV–ZEL'DOVICH AND X-RAY SURVEYS. I. THE INFLUENCE OF FEEDBACK, NON-THERMAL PRESSURE, AND CLUSTER SHAPES ON Y–M SCALING RELATIONS (2011, methodology): “…forming at radii> R200 as suggested by numerical simulations (Miniati et al. 2000; Ryu et al. 2003; Pfrommer et al. 2006b; Skillman et al. 2008; Vazza et al. 2009) or indirectly by the action of shock waves on radio plasma bubbles, which represents a novel method of finding formation shocks…”
Acceleration of primary and secondary particles in galaxy clusters by compressible MHD turbulence: from radio haloes to gamma-rays (2010, background): “…galaxy clusters for a substantial fraction of the period of cluster-cluster interaction, a few Gyr, possibly driven by shock waves that cross the cluster volume and by the sloshing (and stripping) of cluster cores (e.g., Dolag et al. 2005; Vazza et al. 2009a; Paul et al. 2010; ZuHone et al. 2010).”
SEARCH FOR COSMIC-RAY-INDUCED GAMMA-RAY EMISSION IN GALAXY CLUSTERS (2013, background): “The intracluster medium (ICM) consists of a hot (1-10 keV) plasma, which has primarily been heated through collisionless shocks that form as a result of the hierarchical build up of galaxy clusters (e.g., Ryu et al. 2003; Pfrommer et al. 2006; Skillman et al. 2008; Vazza et al. 2009).”