Probing turbulence in the Coma galaxy cluster

Schuecker, P.; Finoguenov, A.; Miniati, Francesco; Böhringer, H.; Briel, U. G.

doi:10.1051/0004-6361:20041039

Cited by 280 publications

(345 citation statements)

References 28 publications

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“…They base their arguments on the observation of very elongated H-α £laments which suggest a laminar ¤ow pattern behind buoyantly rising radio bubbles. An upper limit on the viscosity in the (non-cooling core) Coma cluster of ∼ 3 · 10 29 cm 2 /s is reported by Schuecker et al (2004). Both limits are consistent with our coarse estimate of the large scale viscosity and enclose it.…”

Section: Observationssupporting

confidence: 86%

Magnetic turbulence in cool cores of galaxy clusters

Vogt¹,

Enßlin²

2006

Astron Nachr

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Abstract. We argue that the recently reported Kolmogorov-like magnetic turbulence spectrum in the cool core of the Hydra A galaxy cluster can be understood by kinetic energy injection by active galaxies that drives a turbulent non-helical magnetic dynamo into its saturated state. Although dramatic differences exist between small-scale dynamo scenarios, their saturated state is expected to be similar, as we show for three scenarios: the ¤ux rope dynamo, the ¤uctuation dynamo, and the explosive dynamo. Based on those scenarios, we develop an analytical model of the hydrodynamic and magnetic turbulence in cool cores. The model implies magnetic £eld strengths that £t well with Faraday rotation measurements and minimum energy estimates for the sample of cool core clusters having such data available. Predictions for magnetic £elds in clusters for which the appropriate observational information is still missing, and for yet unobserved quantities like the hydrodynamical turbulence velocity and characteristic length-scale are provided. The underlying dynamo models suggest magnetic intermittency and possibly a largescale hydrodynamic viscosity. We conclude that the success of the model to explain the £eld strength in cool core clusters indicates that in general cluster magnetic £elds directly re¤ect hydrodynamical turbulence, also in clusters without cool cores.

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Section: Observationssupporting

confidence: 86%

Magnetic turbulence in cool cores of galaxy clusters

Vogt¹,

Enßlin²

2006

Astron Nachr

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“…ATHENA) should be able eventually to detect directly the driving-scale turbulent motions in the ICMs of multiple clusters (Nagai et al 2013;Ettori et al 2013;Zhuravleva et al 2013;). In the meantime, turbulent motions in the ICM induce moderate pressure fluctuations that may be detected in X-rays (e.g., Schuecker et al 2004;Sanders & Fabian 2012;Churazov et al 2012;Gaspari et al 2014;Zhuravleva et al 2014), or through the S-Z effect (e.g., Khatri & Gaspari 2016). …”

Section: Discussionmentioning

confidence: 99%

Turbulence and vorticity in Galaxy clusters generated by structure formation

Vazza

Jones

Brüggen

et al. 2016

Mon. Not. R. Astron. Soc.

124

150

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Turbulence is a key ingredient for the evolution of the intracluster medium, whose properties can be predicted with high resolution numerical simulations. We present initial results on the generation of solenoidal and compressive turbulence in the intracluster medium during the formation of a small-size cluster using highly resolved, non-radiative cosmological simulations, with a refined monitoring in time. In this first of a series of papers, we closely look at one simulated cluster whose formation was distinguished by a merger around z ∼ 0.3. We separate laminar gas motions, turbulence and shocks with dedicated filtering strategies and distinguish the solenoidal and compressive components of the gas flows using Hodge-Helmholtz decomposition. Solenoidal turbulence dominates the dissipation of turbulent motions (∼ 95%) in the central cluster volume at all epochs. The dissipation via compressive modes is found to be more important (∼ 30% of the total) only at large radii ( 0.5 r vir ) and close to merger events. We show that enstrophy (vorticity squared) is good proxy of solenoidal turbulence. All terms ruling the evolution of enstrophy (i.e. baroclinic, compressive, stretching and advective terms) are found to be significant, but in amounts that vary with time and location. Two important trends for the growth of enstrophy in our simulation are identified: first, enstrophy is continuously accreted into the cluster from the outside, and most of that accreted enstrophy is generated near the outer accretion shocks by baroclinic and compressive processes. Second, in the cluster interior vortex stretching is dominant, although the other terms also contribute substantially.

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“…Slightly different approaches have been used to measure pressure fluctuations in the Coma Cluster (Schuecker et al 2004) and temperature fluctuations in a sample of clusters (Gu et al 2009). The only difference here from our previous analyzes is that here the 2D → 3D deprojection is calculated at each pixel instead of averaged over an area of interest.…”

Section: Data Processing Images and Power Spectramentioning

confidence: 99%

The nature and energetics of AGN-driven perturbations in the hot gas in the Perseus Cluster

Zhuravleva

Churazov

Arévalo

et al. 2016

Mon. Not. R. Astron. Soc.

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Cores of relaxed galaxy clusters are often disturbed by AGN. Their Chandra observations revealed a wealth of structures induced by shocks, subsonic gas motions, bubbles of relativistic plasma, etc. In this paper, we determine the nature and energy content of gas fluctuations in the Perseus core by probing statistical properties of emissivity fluctuations imprinted in the soft-and hard-band X-ray images. About 80 per cent of the total variance of perturbations on ∼ 8 − 70 kpc scales in the inner region have an isobaric nature, i.e., are consistent with slow displacements of the gas in pressure equilibrium with ambient medium. Observed variance translates to the ratio of nonthermal to thermal energy of ∼ 13 per cent. In the region dominated by weak "ripples", about half of the total variance is also associated with isobaric perturbations on scales a few tens of kpc. If these isobaric perturbations are induced by buoyantly rising bubbles, then these results suggest that most of the AGN-injected energy should first go into bubbles rather than into shocks. Using simulations of a shock propagating through the Perseus atmosphere, we found that models reproducing the observed features of a central shock have more than 50 per cent of the AGN-injected energy associated with the bubble enthalpy and only about 20 per cent is carried away with the shock. Such energy partition is consistent with the AGN-feedback model, mediated by bubbles of relativistic plasma, and supports the importance of turbulence in the balance between gas heating and radiative cooling.

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Probing turbulence in the Coma galaxy cluster

Cited by 280 publications

References 28 publications

Magnetic turbulence in cool cores of galaxy clusters

Magnetic turbulence in cool cores of galaxy clusters

Turbulence and vorticity in Galaxy clusters generated by structure formation

The nature and energetics of AGN-driven perturbations in the hot gas in the Perseus Cluster

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