Halo and relic sources in clusters of galaxies

Giovannini, G.; Feretti, L.

doi:10.1016/s1384-1076(00)00034-8

Cited by 211 publications

(253 citation statements)

References 30 publications

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“…The extended diffuse emission is easily visible. It is similar to small-size asymmetric radio halos found in other clusters such as A2218 (Giovannini & Feretti 2000), and we classify it as a small-size radio halo. However, the diffuse radio source shows a peculiar bright filament in the inner region with a sharp bend as a Z shaped structure.…”

Section: New Radio Halos At 14 Ghzsupporting

confidence: 77%

“…Radio halos at higher redshift are rare. We will present results for higher redshift clusters in a forthcoming paper (but see Giovannini & Feretti 2000;and Bonafede et al 2009b). We have a total of 33 sources; however, in the case of CL1446+26 the diffuse source should be classified as a relic source and in A3444 the giant diffuse emission is likely a giant filament, and the extended emission around the cD galaxy a mini-halo.…”

Section: Discussionmentioning

confidence: 99%

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Radio halos in nearby (z < 0.4) clusters of galaxies

Giovannini

Bonafede

Feretti

et al. 2009

A&A

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170

263

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Context. The intra-cluster medium is characterized by thermal emission, and by the presence of large scale magnetic fields. In some clusters of galaxies, a diffuse non-thermal emission is also present, located at the cluster center and called radio halo. These sources indicate the existence of relativistic particles and magnetic fields in the cluster volume. Aims. In this paper we collect data on all known nearby cluster radio halos (z < 0.4), to discuss their statistical properties and to investigate their origin. Methods. We searched for published data on radio halos and reduced new and archive VLA data to increase the number of known radio halos.Results. We present data on 31 radio halos, 1 new relic source, and 1 giant filament. We note the discovery of a small size diffuse radio emission in a cluster (A1213) with very low X-ray luminosity. Among the statistical results, we confirm the correlation between the average halo radio spectral index and the cluster temperature. We also discuss the high percentage of clusters where both a relic and a radio halo is present. Conclusions. The sample of radio halos discussed here represents the population of radio halos observable with current radio telescopes. A new telescope generation is necessary for a more detailed multifrequency study, and to investigate the possible existence of a population of radio halos with different properties.

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Section: New Radio Halos At 14 Ghzsupporting

confidence: 77%

Section: Discussionmentioning

confidence: 99%

Radio halos in nearby (z < 0.4) clusters of galaxies

Giovannini

Bonafede

Feretti

et al. 2009

A&A

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170

263

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“…Giovannini & Feretti (2000) measured S 1400 MHz = 18.3 mJy. In the absence of a measured index α, we adopt the arbitrary value of α = 1.5 to obtain the magnetic field constraint listed in Table 3.…”

Section: A2142mentioning

confidence: 97%

“…However, evidence gathered at different wavelengths points to the existence of a nonthermal component. In particular, the detection of an extended synchrotron radio emission (e.g., Willson 1970;Harris & Miley 1978;Giovannini et al 1993;Giovannini & Feretti 2000;Kempner & Sarazin 2001;Thierbach et al 2003) and, more recently, of a possibly nonthermal extreme ultraviolet (EUV) excess (Lieu et al 1996;Bowyer et al 1999;Bonamente et al 2001;Durret et al 2002) and soft excess (e.g., Werner et al 2007) suggest the existence of a nonthermal X-ray component originating from a population of relativistic electrons. This scenario is confirmed by the detection of nonthermal emission in the hard X-ray spectra of a few galaxy clusters (see, e.g., Kaastra et al 2008;Rephaeli et al 2008, for a complete review).…”

Section: Introductionmentioning

confidence: 99%

GALAXY CLUSTERS IN THESWIFT/BURST ALERT TELESCOPE ERA: HARD X-RAYS IN THE INTRACLUSTER MEDIUM

Ajello

Rebusco

Cappelluti

et al. 2008

ApJ

101

126

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We report the detection of 10 clusters of galaxies in the ongoing Swift/Burst Alert Telescope (BAT) all-sky survey. This sample, which mostly comprises merging clusters, was serendipitously detected in the 15-55 keV band. We use the BAT sample to investigate the presence of excess hard X-rays above the thermal emission. The BAT clusters do not show significant (e.g., 2σ ) nonthermal hard X-ray emission. The only exception is represented by Perseus whose high-energy emission is likely due to NGC 1275. Using XMM-Newton, Swift/XRT, Chandra and BAT data, we are able to produce upper limits of the inverse Compton (IC) emission mechanism which are in disagreement with most of the previously-claimed hard X-ray excesses. The coupling of the X-ray upper limits of the IC mechanism to radio data shows that, in some clusters, the magnetic field might be larger than 0.5 μG. We also derive the first log N-log S and luminosity function distributions of galaxy clusters above 15 keV.

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“…In a recent VLA survey of 205 nearby clusters in the ACO catalog extended emission was measured in 32 clusters (Giovannini et al 1999(Giovannini et al , 2000. Only about a dozen of these were previously known to have regions of extended radio emission.…”

Section: Radio Emissionmentioning

confidence: 99%

Nonthermal Phenomena in Clusters of Galaxies

Rephaeli¹

2001

Astrophysical Sources of High Energy Particles and Radiation

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Abstract.Recent observations of high energy (> 20 keV) X-ray emission in a few clusters extend and broaden our knowledge of physical phenomena in the intracluster space. This emission is likely to be nonthermal, probably resulting from Compton scattering of relativistic electrons by the cosmic microwave background radiation. Direct evidence for the presence of relativistic electrons in some ∼ 30 clusters comes from measurements of extended radio emission in their central regions. I first review the results from RXTE and BeppoSAX measurements of a small sample of clusters, and then discuss their implications on the mean values of intracluster magnetic fields and relativistic electron energy densities. Implications on the origin of the fields and electrons are briefly considered.

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Halo and relic sources in clusters of galaxies

Cited by 211 publications

References 30 publications

Radio halos in nearby (z < 0.4) clusters of galaxies

Radio halos in nearby (z < 0.4) clusters of galaxies

GALAXY CLUSTERS IN THESWIFT/BURST ALERT TELESCOPE ERA: HARD X-RAYS IN THE INTRACLUSTER MEDIUM

Nonthermal Phenomena in Clusters of Galaxies

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