Strong Turbulence in the Cool Cores of Galaxy Clusters: Can Tsunamis Solve the Cooling Flow Problem?

Fujita, Yutaka; Matsumoto, Toshiro; Wada, Keiichi

doi:10.1086/424483

Cited by 79 publications

(79 citation statements)

References 33 publications

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“…This is consistent with the fact that there is no correlation between the masses of black holes in the central AGNs and the X-ray luminosities of the central regions of the clusters [19]. Alternative idea is that cluster mergers are responsible for heating of cool cores [20,21]. In this "tsunami" model, bulk gas motions excited by cluster mergers produce turbulence in and around a core, because the cooling heavy core cannot be moved by the bulk gas motions, and the resultant relative gas motion between the core and the surrounding gas induces hydrodynamic instabilities.…”

Section: Discussionsupporting

confidence: 78%

The Difficulty of the Heating of Cluster Cooling Flows by Sound Waves and Weak Shocks

Fujita¹,

Suzuki²

2007

Eso Astrophysics Symposia

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We investigate heating of the cool core of a galaxy cluster through the dissipation of sound waves and weak shocks excited by the activities of the central active galactic nucleus (AGN). Using a weak shock theory, we show that this heating mechanism alone cannot reproduce observed temperature and density profiles of a cluster, because the dissipation length of the waves is much smaller than the size of the core and thus the wave energy is not distributed to the whole core.

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Section: Discussionsupporting

confidence: 78%

The Difficulty of the Heating of Cluster Cooling Flows by Sound Waves and Weak Shocks

Fujita¹,

Suzuki²

2007

Eso Astrophysics Symposia

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“…mainly to the heating contributed especially by the improved artificial conductivity. Interestingly, this would provide further support to the role played by turbulence in heating the ICM and therefore compensating radiative cooling (see discussion in V11 and ,e.g., Fujita et al 2004;Fujita 2005).…”

Section: Comparison Between Adiabatic and Radiative Runsmentioning

confidence: 64%

The role of the artificial conductivity in SPH simulations of galaxy clusters: effects on the ICM properties

Biffi

Valdarnini

2014

Monthly Notices of the Royal Astronomical Society

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We study the thermal structure of the intra-cluster medium (ICM) in a set of cosmological hydrodynamical cluster simulations performed with an SPH numerical scheme employing an artificial conductivity (AC) term. We explore the effects of this term on the ICM temperature and entropy profiles, thermal distribution, velocity field and expected X-ray emission. We find that in adiabatic runs the artificial conductivity favours (i) the formation of an entropy core, raising and flattening the central entropy profiles, in better agreement with findings from Eulerian codes; and (ii) a systematic reduction of the cold gas component. In fact, the cluster large-scale structure and dynamical state are preserved across different runs, but the improved gas mixing enabled by the AC term strongly increases the stripping rate of gas from the cold clumps moving through the ICM. This in turn reduces the production of turbulence generated by the instabilities which develop because of the interaction between clumps and ambient ICM. We then find that turbulent motions, enhanced by the time-dependent artificial viscosity scheme we use, are rather damped by the AC term. The ICM synthetic X-ray emission substantially mirrors the changes in its thermo-dynamical structure, stressing the robustness of the AC impact. All these effects are softened by the introduction of radiative cooling but still present, especially a partial suppression of cold gas. Therefore, not only the physics accounted for, but also the numerical approach itself can have an impact in shaping the ICM thermo-dynamical structure and ultimately in the use of SPH cluster simulations for cosmological studies.

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“…These results provide strong support however for the plausibility of models in which radiative cooling in the cluster cores is compensated by turbulent heating of the ICM (Fujita et al 2004b;Fujita 2005). This scenario is observationally motivated by the lack of resonant scattering from X-ray spectra (Churazov et al 2004) as well as by the constraints on diffusion processes extracted from measured iron abundance profiles (Rebusco et al 2006;David & Nulsen 2008), which indicate how the outward diffusion in cluster cores of iron must be driven by turbulent gas motion.…”

Section: Simulations With Cooling and Star Formationmentioning

confidence: 71%

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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Strong Turbulence in the Cool Cores of Galaxy Clusters: Can Tsunamis Solve the Cooling Flow Problem?

Cited by 79 publications

References 33 publications

The Difficulty of the Heating of Cluster Cooling Flows by Sound Waves and Weak Shocks

The Difficulty of the Heating of Cluster Cooling Flows by Sound Waves and Weak Shocks

The role of the artificial conductivity in SPH simulations of galaxy clusters: effects on the ICM properties

The impact of numerical viscosity in SPH simulations of galaxy clusters

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