Radio halos in nearby (<i>z</i> &lt; 0.4) clusters of galaxies

Giovannini, G.; Bonafede, A.; Feretti, L.; Govoni, F.; Murgia, M.; Ferrari, Fabrício; Monti, G.

doi:10.1051/0004-6361/200912667

Cited by 170 publications

(295 citation statements)

References 70 publications

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“…In this paper, we present the properties of the remaining four clusters (A800, A910, A1550, CL1446+26), for which only data at 1.4 GHz are available in the archive. We note that a peripheral diffuse emission, classified as a radio relic, was previously detected in CL1446+26 by Giovannini et al (2009). However, on the basis of the data presented here the classification of the diffuse emission in this cluster is more complex than previously stated.…”

Section: Vla Observations and Data Reductionsupporting

confidence: 50%

“…At radio wavelengths, it was studied by Owen et al (1999) and Giovannini et al (2009). The presence of a northern radio relic plus several radio galaxies were pointed out by Giovannini et al (2009) (see also the radio contours in the bottom-right panel of Fig.…”

Section: +26mentioning

confidence: 87%

“…In the case of CL1446+26, we used the VLA data in C configuration previously analyzed by Giovannini et al (2009).…”

Section: Vla Observations and Data Reductionmentioning

confidence: 99%

“…Giovannini et al 1999;Giovannini & Feretti 2000;Kempner & Sarazin 2001;Govoni et al 2001a;Bacchi et al 2003;Venturi et al 2007;Venturi et al 2008;van Weeren et al 2009;Rudnick & Lemmerman 2009;Giovannini et al 2009;van Weeren et al 2011). These radio sources, which extend over volumes of ∼1 Mpc 3 and are called radio halos, are diffuse, low-surface-brightness ( 1 μJy arcsec −2 at 1.4 GHz), and steepspectrum 1 (α > 1) synchrotron sources with no obvious optical counterparts (see e.g.…”

Section: Introductionmentioning

confidence: 99%

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Detection of diffuse radio emission in the galaxy clusters A800, A910, A1550, and CL 1446+26

Govoni¹,

Ferrari²,

Feretti³

et al. 2012

A&A

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Context. Radio halos are elusive sources located at the center of merging galaxy clusters. To date, only about 40 radio halos are known, thus the discovery of new halos provides important insights into this class of sources. Aims. To improve the quality of the statistics of radio halos, we investigate the radio continuum emission of a sample of galaxy clusters. Methods. We analyzed archival Very Large Array observations at 1.4 GHz, with a resolution of 1 . These observations were complemented by X-ray, optical, and higher-resolution radio data, leading to the detection of a new radio halo in the central region of A800 and A1550. We discovered a radio relic in the periphery of A910, and finally revealed both a halo and a relic in CL1446+26. Results. The clusters hosting these new halos show an offset between the radio and the X-ray peak. By analyzing this offset statistically, we find that radio halos can be quite asymmetric with respect to the X-ray gas distribution, with an average radio-X-ray displacement of about 180 kpc. When the offsets are normalized by the halo size, there is a tendency for smaller halos to have larger displacements.

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Section: Vla Observations and Data Reductionsupporting

confidence: 50%

Section: +26mentioning

confidence: 87%

“…In the case of CL1446+26, we used the VLA data in C configuration previously analyzed by Giovannini et al (2009).…”

Section: Vla Observations and Data Reductionmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

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Detection of diffuse radio emission in the galaxy clusters A800, A910, A1550, and CL 1446+26

Govoni¹,

Ferrari²,

Feretti³

et al. 2012

A&A

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“…The diffuse non-thermal component is now well detected at radio wavelengths in about 30 clusters (Giovannini et al 2009). Only a few X-ray satellites allowed possible but controversial detection of a hard tail in the X-ray spectrum of about ten clusters (see e.g.…”

Section: Introductionmentioning

confidence: 99%

GMRT observations of the Ophiuchus galaxy cluster

Murgia¹,

Eckert

Govoni³

et al. 2010

A&A

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Aims. Observations with the Very Large Array telescope at 1477 MHz revealed the presence of a radio mini-halo surrounding the faint central point-like radio source in the Ophiuchus cluster of galaxies. In this work we present a study of the radio emission from this cluster of galaxies at lower radio frequencies. Methods. We observed the Ophiuchus cluster at 153, 240, and 614 MHz with the Giant Metrewave Radio Telescope. Results. The mini-halo is clearly detected at 153 and 240 MHz, the frequencies at which we reached the best sensitivity to the lowsurface brightness diffuse emission, while it is not detected at 610 MHz because of the too low signal-to-noise ratio at this frequency. The most prominent feature at low frequencies is a patch of diffuse steep spectrum emission located at about 5 south-east from the cluster centre. By combining these images with that at 1477 MHz, we derived the spectral index of the mini-halo. Globally, the minihalo has a low-frequency spectral index of α 153 240 1.4 ± 0.3 and an high-frequency spectral index of α 240 1477 1.60 ± 0.05. Moreover, we measure a systematic increase of the high-frequency spectral index with radius: the azimuthal radial average of α 240 1477 increases from about 1.3, at the cluster centre, up to about 2.0 in the mini-halo outskirts. Conclusions. The observed radio spectral index agrees with that obtained by modelling the non-thermal hard X-ray emission in this cluster of galaxies. We assume that the X-ray component arises from inverse-Compton scattering between the photons of the cosmic microwave background and a population of non-thermal electrons, which are isotropically distributed and whose energy spectrum is a power law with an index p. We derive that the electrons energy spectrum should extend from a minimum Lorentz factor of γ min 700 up to a maximum Lorentz factor of γ max 3.8 × 10 4 with an index p = 3.8 ± 0.4. The volume-averaged strength for a completely disordered intra-cluster magnetic field is B V 0.3 ± 0.1 μG.

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Some results on the radio‐SZ correlation for galaxy cluster radio halos

Basu

2013

Astron Nachr

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We present correlation results for the radio halo power in galaxy clusters with the integrated thermal Sunyaev-Zel'dovich (SZ) effect signal, including new results obtained at sub-GHz frequencies. The radio data is compiled from several published works, and the SZ measurements are taken from the Planck ESZ cluster catalog. The tight correlation between the radio halo power and the SZ effect demonstrates a clear correspondence between the thermal and non-thermal electron populations in the intra-cluster medium, as already has been shown in X-ray based studies. The radio power varies roughly as the square of the global SZ signal, but when the SZ signal is scaled to within the radio halo radius the correlation becomes approximately linear, with reduced intrinsic scatter. We do not find any strong indication of a bi-modal division in the radio halo cluster population, as has been reported in the literature, which suggests that such duality could be an artifact of X-ray selection. We compare the SZ signal dependence of radio halos with simplified predictions from theoretical models, and discuss some implications and shortcomings of the present work.Comment: To be published in the Astronomische Nachrichten (AN); proceeding article for the XMM-Newton 2012 science workshop: "Galaxy Clusters as Giant Cosmic Laboratories

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

Cited by 170 publications

References 70 publications

Detection of diffuse radio emission in the galaxy clusters A800, A910, A1550, and CL 1446+26

Detection of diffuse radio emission in the galaxy clusters A800, A910, A1550, and CL 1446+26

GMRT observations of the Ophiuchus galaxy cluster

Some results on the radio‐SZ correlation for galaxy cluster radio halos

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