Cosmological Shock Waves and Their Role in the Large-Scale Structure of the Universe

By Dongsu Ryu, Hyesung Kang, E. Hallman, T. W. Jones. 2003

390 citations recorded by the source corpus.

We study the properties of cosmological shock waves identified in high-resolution, N-body/hydrodynamic simulations of a ΛCDM universe and their role on thermalization of gas and acceleration of nonthermal, cosmic-ray (CR) particles. External shocks form around sheets, filaments, and knots of mass distribution when the gas in void regions accretes onto them. Within those nonlinear structures, internal shocks are produced by infall of previously shocked gas to filaments and knots and during subclump mergers, as well as by chaotic flow motions. Due to the low temperature of the accreting gas, the Mach number of external shocks is high, extending up to M ~ 100 or higher. In contrast, internal shocks have mostly low Mach numbers. For all shocks of M ≥ 1.5, the mean distance between shock surfaces over the entire computed volume is ~4 h-1 Mpc at present, or ~1 h-1 Mpc for internal shocks within nonlinear structures. Identified external shocks are more extensive, with their surface area ~2 times larger than that of identified internal shocks at present. However, especially because of higher preshock densities but also due to higher shock speeds, internal shocks dissipate more energy. Hence, the internal shocks are mainly responsible for gas thermalization as well as CR acceleration. In fact, internal shocks with 2 ≲ M ≲ 4 contribute about one-half of the total dissipation. Using a nonlinear diffusive shock acceleration model for CR protons, we estimate the ratio of CR energy to gas thermal energy dissipated at cosmological shock waves to be about one-half through the history of the universe. Our result supports scenarios in which the intracluster medium contains energetically significant populations of CRs.

Subfields: Astronomy and Astrophysics, Nuclear and High Energy Physics

View Paper: https://www.semanticscholar.org/paper/45fa7bb6df28070c51904526e5dbe2b1a31a86f0

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Citations in the corpus

The case for electron re-acceleration at galaxy cluster shocks (2017, background): “However, given the low count rates, it is not possible to extract detailed information on the thermal properties of the ICM in this region.”
DIFFUSIVE SHOCK ACCELERATION SIMULATIONS OF RADIO RELICS (2012, background): “Hot ICMs, on the other hand, should have gone first through accretion shocks of high Mach numbers around clusters and filaments and then through weaker shocks inside those nonlinear structures (Ryu et al. 2003; Kang et al. 2007).”
Cosmic ray feedback in hydrodynamical simulations of galaxy formation (2006, methodology): “…that the strongest shocks occur at low to moderate overdensities in the accretion regions around halos and filaments (Kang et al., 1996; Quilis et al., 1998; Miniati, 2002; Ryu et al., 2003; Pfrommer et al., 2006), and also with the growing importance of cosmic ray loss processes at high densities.”
Cosmological Shocks in Adaptive Mesh Refinement Simulations and the Acceleration of Cosmic Rays (2008, methodology): “In our analysis, as in Ryu et al. (2003), we have set a minimum preshock temperature of T = 104K since the low-density gas in our cosmological simulations is assumed to be ionized (a reasonable assumption at z .”
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).”
Simulating cosmic rays in clusters of galaxies – II. A unified scheme for radio haloes and relics with predictions of the γ-ray emission (2007, background): “In contrast, Ryu et al. (2003) and Pfrommer et al. (2006) found that the Mach number distribution peaks in the range 1.”
Detecting shock waves in cosmological smoothed particle hydrodynamics simulations (2006, methodology): “We classify cosmological shock waves as internal and external shocks, depending on whether or not the associated pre-shock gas was previously shocked (cf. Ryu et al. 2003).”
Turbulent Motions and Shocks Waves in Galaxy Clusters simulated with AMR (2009, background): “The thermal energy flux across shocks is customary evaluated as: fth = δM(M) · ρM3v3s/2, (6) whereρ is the pre-shock density andδM(M) is a monotonically increasing function ofM (e.g. Ryu et al.2003).”
Radio signature of cosmological structure formation shocks (2006, background): “Numerical simulations suggest that structure formation shocks may be subdivided into two classes (Ryu et al. 2003).”
Alfvénic reacceleration of relativistic particles in galaxy clusters: MHD waves, leptons and hadrons (2003, background): “Moreover, the numerical simulations of Ryu et al. (2003) also find a class of high Mach number shocks that are related to gravitationally unbound structures, not included in semi-analytical calculations.”
Science with the Murchison Widefield Array (2012, background): “Theory suggests that the infall of baryons into the cosmic web results in high Mach number intergalactic shocks (e.g., Cen & Ostriker 1999; Ryu et al. 2003).”
Acceleration of primary and secondary particles in galaxy clusters by compressible MHD turbulence: from radio haloes to gamma-rays (2010, background): “…particles via shocks and turbulence (e.g. Ensslin et al 1998; Sarazin 1999; Blasi 2001; Brunetti et al. 2001, 2004; Petrosian 2001; Miniati et al. 2001; Fujita et al 2003; Gabici & Blasi 2003; Ryu et al. 2003; Cassano & Brunetti 2005; Hoeft & Bruggen 2007; Brunetti & Lazarian 2007; Pfrommer 2008).”
Cluster Mergers and Non-Thermal Phenomena: A Statistical Magneto-Turbulent Model (2004, background): “On the other hand, more recent numerical simulations find more weak shocks with the bulk of the energy dissipation (thermal energy and cosmic rays) in internal shocks with 2 M 4 (Ryu et al. 2003).”
A Physical Relationship between Electron-Proton Temperature Equilibration and Mach Number in Fast Collisionless Shocks (2006, background): “Collisionless shocks play a dominant role in heating the intergalactic medium (IGM) during large scale structure formation (Ryu et al. 2003; Yoshida et al. 2005; Kang et al. 2005).”
Comparing AMR and SPH Cosmological Simulations. I. Dark Matter and Adiabatic Simulations (2003, background): “As time progresses, virialized halos and dark matter filaments form, which are surrounded by strong accretion shocks in the gas and are filled with weaker flow shocks (Ryu et al. 2003).”
Shock waves in Eulerian cosmological simulations: main properties and acceleration of cosmic rays (2008, methodology): “Because a mass deficit in cluster haloes may introduce a deficit in the energy processed by shocks in the total simulated volume, this should be taken into account when we compare our results with previous studies (e.g. Ryu et al. 2003; Pfrommer et al. 2006; Kang et al. 2007).”