A Multifiltering Study of Turbulence in a Large Sample of Simulated Galaxy Clusters

Abstract

We present results from a large set of N-body/SPH hydrodynamical cluster simulations aimed at studying the statistical properties of turbulence in the ICM. The numerical hydrodynamical scheme employs a SPH formulation in which gradient errors are strongly reduced by using an integral approach. We consider both adiabatic and radiative simulations. We construct clusters subsamples according to the cluster dynamical status or gas physical modeling, from which we extract small-scale turbulent velocities obtained by applying to cluster velocities different multiscale filtering methods. The velocity power spectra of non-radiative relaxed clusters are mostly solenoidal and exhibit a peak at wavenumbers set by the injection scales ≃ r 200 /10, at higher wavenumbers the spectra are steeper than Kolgomorov. Cooling runs are distinguished by much shallower spectra, a feature which we interpret as the injection of turbulence at small scales due to the interaction of compact cool gas cores with the ICM. Turbulence in galaxy clusters is then characterized by multiple injection scales, with the small scale driving source acting in addition to the large scale injection mechanisms. Cooling runs of relaxed clusters exhibit enstrophy profiles with a power-law behavior over more than two decades in radius, and a turbulent-to-thermal energy ratio < ∼ 1%. In accord with Hitomi observations, in the core of a highly relaxed cluster we find low level of gas motions. In addition, the estimated cluster radial profile of the sloshing oscillation period is in very good agreement with recent Fornax measurements, with the associated Froude number satisfying F r < ∼ 0.1 within r/r 200 < ∼ 0.1. Our findings suggest that in cluster cores ICM turbulence approaches a stratified anisotropic regime, with weak stirring motions dominated by gravity buoyancy forces and strongly suppressed along the radial direction. We conclude that turbulent heating cannot be considered the main heating source in cluster cores.

Einstein, Planck and Vera Rubin: Relevant Encounters Between the Cosmological and the Quantum Worlds

“…The implementation of an Everett phone deserves further investigations and is currently under study [257] together with the search for a general proof of the existence of gravity induced correlations between the different branches of the wave function within a path integral formulation of the NNG model a' la Feynman-Vernon [258]. We strongly believe that this issue will help to clarify the role of gravity induced de-coherence in wave function collapse and stimulate to look for the answer to a further question: how to discriminate in principle this kind of fundamental de-coherence against the usual environmental decoherence and, finally, how to experimentally detect such a difference.…”

“…The author [259] presented results from a large set of N-body/SPH hydrodynamical cluster simulations aimed at studying the statistical properties of turbulence in the ICM (InterGalactic Cluster Medium). The cosmological model is a flat CDM model, with vacuum energy density Ω Λ 0.7, matter density parameter Ω m 0.3 and Hubble constant h 0.7 H 0 /(100 km sec − 1 Mpc − 1 ).…”

“…We construct clusters subsamples according to the cluster dynamical status or gas physical modeling. We quantify the cluster dynamical state by using, as a morphological indicator, the power ratio method [259]. According to this method, the projected X-ray surface brightness Σ X ( x → ) is the source term of the pseudo potential Ψ( x → ) which satisfies the 2-D Poisson equation.…”

AGN jet feedback on a moving mesh: lobe energetics and X-ray properties in a realistic cluster environment

“…Dolag et al 2005;Vazza et al 2009;Valdarnini 2011) or multi-scale filtering (e.g. Vazza et al 2012Vazza et al , 2017Bourne & Sijacki 2017;Valdarnini 2019), given the small fraction of injected energy retained in the kinetic form within the lobes (see below), the turbulent component can only be comparable or less than this i.e. also a small contribution to the total energy budget.…”

Towards mapping turbulence in the intra-cluster medium

“…Numerical simulations indicate a change in the morphology of turbulent fields in regions showing strong density gradients (e.g. Shi & Zhang 2019), even in cluster cores (Valdarnini 2019). According to these findings, one can therefore expect our model to become less representative as larger and larger cluster radii enter the emission line analysis, or in the presence of strong cool-core clusters.…”