Massive and refined: A sample of large galaxy clusters simulated at high resolution. I: Thermal gas and properties of shock waves

Abstract Cosmological shock waves are ubiquitous to cosmic structure formation and evolution. As a consequence, they play a major role in the energy distribution and thermalization of the intergalactic medium (IGM). We analyse the Mach number distribution in the Dianoga simulations of galaxy clusters performed with the SPH code GADGET-3. The simulations include the effects of radiative cooling, star formation, metal enrichment, supernova and active galactic nuclei feedback. A grid-based shock-finding algorithm is applied in post-processing to the outputs of the simulations. This procedure allows us to explore in detail the distribution of shocked cells and their strengths as a function of cluster mass, redshift and baryonic physics. We also pay special attention to the connection between shock waves and the cool-core/non-cool core (CC/NCC) state and the global dynamical status of the simulated clusters. In terms of general shock statistics, we obtain a broad agreement with previous works, with weak (low-Mach number) shocks filling most of the volume and processing most of the total thermal energy flux. As a function of cluster mass, we find that massive clusters seem more efficient in thermalising the IGM and tend to show larger external accretion shocks than less massive systems. We do not find any relevant difference between CC and NCC clusters. However, we find a mild dependence of the radial distribution of the shock Mach number on the cluster dynamical state, with disturbed systems showing stronger shocks than regular ones throughout the cluster volume.

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Profiles of Galaxy Clusters in Cosmological Scenarios

Symposium - International Astronomical Union ◽

10.1017/s0074180900150363 ◽

1987 ◽

Vol 117 ◽

pp. 287-287

Author(s):

Michael J. West ◽

Avishai Dekel ◽

Augustus Oemler

Keyword(s):

High Resolution ◽

Galaxy Clusters ◽

Hierarchical Clustering ◽

Large Scale ◽

Power Spectra ◽

Clusters Of Galaxies ◽

Spatial Symmetry ◽

Abell Clusters ◽

Wide Range ◽

Large Scale Simulations

We have studied the properties of rich clusters of galaxies in various cosmological scenarios by comparing high resolution N-body simulations with observations of Abell clusters. The clusters have been simulated in two steps. First, protoclusters are identified in large-scale simulations which represent a wide range of cosmological scenarios (hierarchical clustering, pancake scenarios, and hybrids of the two, spanning a range of power spectra). Then the region around each protocluster is simulated with high resolution, the particles representing L* galaxies. The protoclusters have no spatial symmetry built into them initially. The final clusters are still dynamically young, and of moderate densities, which should be representative of Abell clusters of richness classes 1 and 2.

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Inverse Energy Cascade of Fast Magnetosonic Turbulence in the Heliosheath

10.5194/egusphere-egu2020-12219 ◽

2020 ◽

Author(s):

Bertalan Zieger

Keyword(s):

Solar Wind ◽

High Resolution ◽

Shock Waves ◽

High Frequency ◽

Collisionless Plasma ◽

Energy Cascade ◽

Fast Mode ◽

Turbulence Spectrum ◽

Inverse Energy Cascade ◽

Voyager 2

The solar wind in the heliosheath beyond the termination shock (TS) is a non-equilibrium collisionless plasma consisting of thermal solar wind ions, suprathermal pickup ions (PUI) and electrons. In such multi-ion plasma, two fast magnetosonic wave modes exist: the low-frequency fast mode that propagates in the thermal ion component and the high-frequency fast mode that propagates in the suprathermal PUI component [Zieger et al., 2015]. Both fast modes are dispersive on fluid and ion scales, which results in nonlinear dispersive shock waves. In this talk, we briefly review the theory of dispersive shock waves in multi-ion collisionless plasma. We present high-resolution three-fluid simulations of the TS and the heliosheath up to 2.2 AU downstream of the TS. We show that downstream propagating nonlinear magnetosonic waves grow until they steepen into shocklets (thin current sheets), overturn, and start to propagate backward in the frame of the downstream propagating wave, as predicted by theory [McKenzie et al., 1993; Dubinin et al., 2006]. The counter-propagating nonlinear waves result in fast magnetosonic turbulence far downstream of the shock. Since the high-frequency fast mode is positive dispersive on fluid scale, energy is transferred from small scales to large scales (inverse energy cascade). Thermal solar wind ions are preferentially heated by the turbulence. Forward and reverse shocklets in the heliosheath can efficiently accelerate both ions and electrons to high energies through the shock drift acceleration mechanism. We validate our three-fluid simulations with in-situ high-resolution Voyager 2 magnetic field and plasma observations at the TS and in the heliosheath. Our simulations reproduce the magnetic turbulence spectrum with a spectral slope of -5/3 observed by Voyager 2 in frequency domain [Fraternale et al., 2019]. However, since Taylor&#8217;s hypothesis is not true for fast magnetosonic perturbations in the heliosheath, the inertial range of the turbulence spectrum is not a Kolmogorov spectrum in wave number domain.&#160;

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COSMOLOGICAL SHOCK WAVES IN THE LARGE SCALE STRUCTURE OF THE UNIVERSE

International Journal of Modern Physics Conference Series ◽

10.1142/s2010194513011653 ◽

2013 ◽

Vol 23 ◽

pp. 386-390

Author(s):

RENYI MA ◽

DONGSU RYU ◽

HYESUNG KANG

Keyword(s):

Shock Waves ◽

Galaxy Clusters ◽

Large Scale ◽

Gamma Ray ◽

High Redshift ◽

Cosmic Ray ◽

Large Scale Structure ◽

Scale Structure ◽

Weak Shocks ◽

The Universe

Based on the cosmological hydrodynamic simulation, we study the properties of shock waves formed during the formation of the large scale structure (LSS) of the universe, and investigate their contribution to the cosmic ray (CR) fraction in the intergalactic medium (IGM). It is found that while strong accretion shocks prevail at high redshift, weak internal shocks become dominant in the intracluster medium (ICM) as galaxy clusters form and virialize at low redshift, z < 1. The accumulated CR proton energy is likely to be less than 10 % of the thermal energy in the ICM, since weak shocks of M ≲ 3 are most abundant. This is consistent with the upper limit constrained by radio and gamma-ray observations of galaxy clusters. In the warm-hot medium (WHIM) inside filaments, CRs and gas could be almost in energy equipartition, since relatively stronger shocks of 5 ≲ M ≲ 10 are dominant there. We suggest that the non-thermal emissions from the CR electrons and protons accelerated by cosmological shock waves could provide a new way to detect the WHIM of the universe.

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