The mixing and transport properties of the intra cluster medium: a numerical study using tracers particles

Vazza, Franco; Gheller, C.; Brunetti, G.

doi:10.1051/0004-6361/200913464

Cited by 39 publications

(65 citation statements)

References 104 publications

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“…Values in the same range are measured in the virial volume of the other two clusters. These results agree with the estimates of turbulent diffusion of previous studies of the simulated ICM using tracers (Vazza et al 2010b) and imply that the efficiency of particle transport in these simulated clusters is much higher than that caused by thermal diffusion (e.g. Shtykovskiy & Gilfanov 2010).…”

Section: Turbulent Diffusion In Clusterssupporting

confidence: 90%

“…In Fig. 12 we show the spectra for three clusters (E1 at z = 0.6, H1 and H5 at z = 0) with a zero-padding technique and employing an apodisation function to avoid spurious effects at the edges of the domain (Vazza et al 2010b;Valdarnini 2011). The wavenumbers are normalised to the virial radius of each cluster, k 0 = 2π/R vir .…”

Section: Power Spectra Of Turbulence In Clustersmentioning

confidence: 99%

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Turbulence in the ICM from mergers, cool-core sloshing, and jets: results from a new multi-scale filtering approach

Vazza

Röediger

Brüggen

2012

A&A

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104

101

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We have designed a simple multi-scale method that identifies turbulent motions in hydrodynamical grid simulations. The method does not assume any a priori coherence scale to distinguish laminar and turbulent flows. Instead, the local mean velocity field around each cell is reconstructed with a multi-scale filtering technique, yielding the maximum scale of turbulent eddies by means of iterations. The method is robust, fast, and easily applicable to any grid simulation. We present here the application of this technique to the study of spatial and spectral properties of turbulence in the intra-cluster medium, measuring turbulent diffusion and anisotropy of the turbulent velocity field for a variety of driving mechanisms: a) accretion of matter in galaxy clusters (simulated with ENZO); b) sloshing motions around cool-cores (simulated with FLASH); c) jet outflows from active galactic nuclei (AGN, simulated with FLASH). The turbulent velocities driven by matter accretion in galaxy clusters are mostly tangential in the inner regions (inside the cluster virial radius) and isotropic in regions close to the virial radius. The same is found for turbulence excited by cool-core sloshing, while the jet outflowing from AGN drives mostly radial turbulence motions near its sonic point and beyond. Turbulence leads to a diffusivity in the range D turb ∼ 10 29 −10 30 cm 2 s −1 in the intra-cluster medium. On average, the energetically dominant mechanism of turbulence driving in the intra cluster medium is represented by accretion of matter and major mergers during cluster evolution.

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Section: Turbulent Diffusion In Clusterssupporting

confidence: 90%

Section: Power Spectra Of Turbulence In Clustersmentioning

confidence: 99%

Turbulence in the ICM from mergers, cool-core sloshing, and jets: results from a new multi-scale filtering approach

Vazza

Röediger

Brüggen

2012

A&A

Self Cite

104

101

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“…For tests about the numerical convergence of this method and a comparison with the more standard refinement based on gas/DM over-density, we address the readers to our previous works (e.g. Vazza et al 2009b;Vazza 2010b).…”

Section: Clusters Simulationsmentioning

confidence: 99%

“…Iapichino & Niemeyer 2008;Vazza et al 2009b;Vazza et al 2010b). Furthermore, the adoption of subgrid modeling to treat the dynamical role played by unresolved gas motions helps us to model the motions more accurately, although their importance in the context of galaxy clusters remains qquite unclear (e.g.…”

Section: Introductionmentioning

confidence: 99%

Massive and refined

Vazza

Brunetti

Gheller

et al. 2011

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We study the properties of chaotic motions in the intra cluster medium using a set of 20 galaxy clusters simulated with large dynamical range, using the adaptive mesh refinement code ENZO. The adopted setup allows us to study the spectral and spatial properties of turbulent motions in galaxy clusters with unprecedented detail, achieving an maximum available Reynolds number of the order of R e ∼ 500−1000 for the largest eddies. We investigated the correlations between the energy of these motions in the intra cluster medium and the dynamical state of the host systems. We find that the statistical properties of turbulent motions and their evolution with time imply that major merger events are responsible for the injection of the bulk of turbulent kinetic energy into the cluster. Turbulence is found to account for ∼20−30 per cent of the thermal energy in merging clusters, and ∼5 per cent in relaxed clusters. We compare the energies of turbulence and motions in our simulated clusters with upper-limits for real nearby clusters derived from XMM-Newton data. When turbulent motions are compared on the same spatial scales, the data from simulations are well within the range presently allowed by observations. Finally, we comment on the possibility that turbulence may accelerate relativistic particles leading to the formation of giant radio halos in turbulent (merging) clusters. On the basis of our simulations, we confirm the conclusions of previous semi-analytical studies that the fraction of turbulent clusters appears to be consistent with that of clusters hosting radio halos.

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“…The development of adaptative mesh refinement (AMR) methods, in which the spatial resolution of the Eulerian grid is locally refined according to some selection criterion (Berger & Colella 1989;Kravtsov et al 1997;Norman 2005), led to a substantial increase in the dynamic range of cosmological simulations of galaxy clusters and a better capability of following the production of turbulence in the ICM induced by merger events (Iapichino & Niemeyer 2008;Maier et al 2009;Vazza et al 2009Vazza et al , 2010.…”

Section: Introductionmentioning

confidence: 99%

The impact of numerical viscosity in SPH simulations of galaxy clusters

Valdarnini

2011

A&A

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The goal of this paper is to investigate in N-body/SPH hydrodynamical cluster simulations the impact of artificial viscosity on the ICM thermal and velocity field statistical properties. To properly reduce the effects of artificial viscosity, a time-dependent artificial viscosity scheme is implemented in an SPH code in which each particle has its own viscosity parameter, whose time evolution is governed by the local shock conditions. The new SPH code is verified in a number of test problems with known analytical or numerical reference solutions and is then used to construct a large set of N-body/SPH hydrodynamical cluster simulations. These simulations are designed to study in SPH simulations the impact of artificial viscosity on the thermodynamics of the ICM and its velocity field statistical properties by comparing results extracted at the present epoch from runs with different artificial viscosity parameters, cluster dynamical states, numerical resolution, and physical modeling of the gas. Spectral properties of the gas velocity field are investigated by measuring the velocity power spectrum E(k) for the simulated clusters. Over a limited range, the longitudinal component E c (k) exhibits a Kolgomorov-like scaling ∝k −5/3 , whilst the solenoidal power spectrum component E s (k) is strongly influenced by numerical resolution effects. The dependence of the spectra E(k) on dissipative effects is found to be significant at length scales < ∼ 100−300 kpc, with viscous damping of the velocities being less pronounced in the runs with the lowest artificial viscosity. The turbulent energy density radial profile E turb (r) is strongly affected by the numerical viscosity scheme adopted in the simulations, with the turbulent-to-total energy density ratios being higher in the runs with the lowest artificial viscosity settings and lying in the range between a few percent and ∼10%. These values are in accord with the corresponding ratios extracted from previous cluster simulations based on mesh-based codes. The radial entropy profiles show a weak dependence on the artificial viscosity parameters of the simulations, with a small amount of entropy mixing being present in cluster cores. At large cluster radii, the mass correction terms to the hydrostatic equilibrium equation are affected little by the numerical viscosity of the simulations, indicating that the X-ray mass bias is already accurately estimated in standard SPH simulations. The results presented here indicate that in individual SPH cluster simulations at least N > ∼ 256 3 gas particles are necessary to provide a correct description of turbulent spectral properties over a decade in wavenumbers, whilst radial profiles of thermodynamic variables can be reliably obtained using N > ∼ 64 3 particles. Finally, simulations in which the gas can cool radiatively are characterized by the presence in the cluster inner regions of high levels of turbulence, generated by the interaction of the compact cool gas core with the ambient medium. These findings strongly support t...

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The mixing and transport properties of the intra cluster medium: a numerical study using tracers particles

Cited by 39 publications

References 104 publications

Turbulence in the ICM from mergers, cool-core sloshing, and jets: results from a new multi-scale filtering approach

Turbulence in the ICM from mergers, cool-core sloshing, and jets: results from a new multi-scale filtering approach

Massive and refined

The impact of numerical viscosity in SPH simulations of galaxy clusters

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