Simulating large‐scale structure formation with magnetic fields

Dolag, K.

doi:10.1002/asna.200610595

Cited by 29 publications

(37 citation statements)

References 45 publications

(55 reference statements)

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“…Dolag 2006;Dubois & Teyssier 2008;Dolag & Stasyszyn 2009;Donnert et al 2009;Collins et al 2010), even if without affecting the spectral properties outlined in Sect. 3.3 for a wide range of scales (e.g.…”

Section: Discussionmentioning

confidence: 99%

Massive and refined

Vazza

Brunetti

Gheller

et al. 2011

A&A

197

292

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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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Section: Discussionmentioning

confidence: 99%

Massive and refined

Vazza

Brunetti

Gheller

et al. 2011

A&A

197

292

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“…In Col. (1) reproduced provided that also the magnetic field scales with cluster mass, temperature or luminosity (e.g. Dolag & Ensslin 2000;Miniati et al 2001;Cassano et al 2006;Dolag 2006).…”

Section: Evolution Of Radio Halos and Connection With Cluster Mergersmentioning

confidence: 99%

“…Consequently, assuming that the ICM is magnetised at μG level, radio halos generated by secondary emission are expected long-living and common; also, some trend between their radio power and the X-ray luminosity or temperature of the hosting clusters is expected (Dolag & Ensslin 2000;Miniati et al 2001;Dolag 2006;Pfrommer et al 2008). Due to the huge uncertainties in the physics of shock acceleration one may easily believe that large variations of the content of relativistic protons are possible among clusters with similar mass (temperature...), however there is no reason to expect a bi-modality in the cluster synchrotron emission.…”

Section: Hadronic Modelsmentioning

confidence: 99%

On the evolution of giant radio halos and their connection with cluster mergers

Brunetti¹,

Cassano²,

Dolag

et al. 2009

A&A

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Aims. Giant radio halos are diffuse, Mpc-scale, synchrotron sources located in the central regions of galaxy clusters and provide the most relevant example of cluster non-thermal activity. Radio and X-ray surveys allow to investigate the statistics of radio halos and may contribute to constrain the origin of these sources and their evolution. Methods. We investigate the distribution of clusters in the plane X-ray (thermal, L X ) vs. synchrotron (non-thermal, P 1.4 ) luminosity, where clusters hosting giant radio halos trace the P 1.4 -L X correlation and clusters without radio halos populate a region that is well separated from that spanned by the above correlation. The connection between radio halos and cluster mergers suggests that the cluster Mpc-scale synchrotron emission is amplified during these mergers and then suppressed when clusters become more dynamically relaxed. Results. In this context, by analysing the distribution in the P 1.4 -L X plane of galaxy clusters from X-ray selected samples with adequate radio follow up, we constrain the typical time-scale of evolution of diffuse radio emission in clusters and discuss the implications for the origin of radio halos. Conclusions. We conclude that cluster synchrotron emission is suppressed (and amplified) in a time-scale significantly smaller than 1 Gyr. We show that this constraint appears difficult to reconcile with the hypothesis that the halo's radio power is suppressed due to dissipation of magnetic field in galaxy clusters. On the other hand, in agreement with models where turbulent acceleration plays a role, present constraints suggest that relativistic electrons are accelerated in Mpc-scale regions, in connection with cluster mergers and for a time-interval of about 1 Gyr, and then they cool in a relatively small time-scale, when the hosting cluster becomes more dynamically relaxed.

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“…This correlation is not subjected to selection effects, at least for high X-ray luminosities (Log(L X ) > 44.6 erg/s; e.g., Clarke 2005;Dolag 2006;) and it implies that the average brightness of RHs increases with the X-ray luminosity of the parent cluster (Feretti 2005;CBS06). If we scale the radio brightness with the cluster X-ray luminosity, the sensitivity limit in radio surveys will set the minimum surface brightness of a RH to be detected, and then a limiting X-ray luminosity of the hosting clusters.…”

Section: The Xbac-nvss Subsamplementioning

confidence: 99%

Revised statistics of radio halos and the reacceleration model

Cassano

Brunetti

Venturi

et al. 2008

A&A

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Aims. The statistical properties of radio halos can be used to discriminate among the possible models for their origin. Therefore, an unbiased and exhaustive investigation of these properties is crucial. Methods. With this goal in mind, in this paper, we revise the occurrence of radio halos in the redshift range 0−0.4, combining the low redshift (z < 0.2) statistical study of the X-ray-brightest Abell-type clusters (XBACs) with the NRAO VLA Sky Survey (NVSS, by Giovannini et al. 1999) with our recent results from the radio followup of the ROSAT-ESO Flux-Limited X-Ray (REFLEX) clusters and extended ROSAT Brightest Cluster Sample (eBCS), i.e., the Giant Metrewave Radio Telescope (GMRT) radio halo survey, at higher redshift (0.2 < z < 0.4). Results. We find significant statistical evidence (at 3.7σ) of an increase of the fraction of clusters with radio halos with the X-ray luminosity (mass) of the parent clusters, and show that this increase is in line with statistical calculations based on the reacceleration scenario. We argue that a fundamental expectation of this scenario is that the probability of having radio halos emitting at hundred MHz is larger than the probability at GHz frequencies, and thus future radio interferometers operating at low frequencies, such as the Low Frequency Array (LOFAR) and the Long Wavelength Array (LWA), should detect a larger number of radio halos with respect to those caught by present GHz observations. We also show that the expected increase of the fraction of clusters with radio halos with the cluster mass as measured with future LOFAR and LWA surveys should be less strong than the increase in present surveys.

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Simulating large‐scale structure formation with magnetic fields

Cited by 29 publications

References 45 publications

Massive and refined

Massive and refined

On the evolution of giant radio halos and their connection with cluster mergers

Revised statistics of radio halos and the reacceleration model

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