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Large-scale magnetic fields reveal themselves through diffuse synchrotron sources observed in galaxy clusters such as radio halos. Total intensity filaments of these sources have been observed in polarization as well, but only in three…

We study the structure of the galaxy cluster Abell 523 (A523) at z=0.104 using new spectroscopic data for 132 galaxies acquired at the Telescopio Nazionale Galileo, new photometric data from the Isaac Newton Telescope, and X-ray and radio…

Astrophysics of Galaxies · Physics 2016-01-27 M. Girardi , W. Boschin , F. Gastaldello , G. Giovannini , F. Govoni , M. Murgia , R. Barrena , S. Ettori , M. Trasatti , V. Vacca

Synchrotron radio emission is being detected from an increasing number of galaxy clusters. Spectral index images are a powerful tool to investigate the origin, nature, and connection of these sources with the dynamical state of the cluster.…

Cosmology and Nongalactic Astrophysics · Physics 2015-06-17 V. Vacca , L. Feretti , G. Giovannini , F. Govoni , M. Murgia , R. A. Perley , T. E. Clarke

Abell 1033 is a merging galaxy cluster of moderate mass ($M_{500}=3.2\times10^{14} \mathrm{M}_\odot$). It hosts a broad variety of diffuse radio sources linked to different astrophysical phenomena. The most peculiar one is an elongated…

Cosmology and Nongalactic Astrophysics · Physics 2022-09-28 H. W. Edler , F. de Gasperin , G. Brunetti , A. Botteon , V. Cuciti , R. J. van Weeren , R. Cassano , T. W. Shimwell , M. Brüggen , A. Drabent

In this paper we present new high sensitivity 153 MHz Giant Meterwave Radio Telescope follow-up observations of the diffuse steep spectrum cluster radio sources in the galaxy clusters Abell 521, Abell 697, Abell 1682. Abell 521 hosts a…

Cosmology and Nongalactic Astrophysics · Physics 2015-06-12 G. Macario , T. Venturi , H. T. Intema , D. Dallacasa , G. Brunetti , R. Cassano , S. Giacintucci , C. Ferrari , C. H. Ishwara-Chandra , R. Athreya

A number of radio observations have revealed the presence of large synchrotron-emitting sources associated with the intra-cluster medium. There is strong observational evidence that the emitting particles have been (re-)accelerated by…

In a recent paper we reported on the discovery of a radio halo with very steep spectrum in the merging galaxy cluster Abell 521 through observations with the Giant Metrewave Radio Telescope (GMRT). We showed that the steep spectrum of the…

Cosmology and Nongalactic Astrophysics · Physics 2015-05-13 D. Dallacasa , G. Brunetti , S. Giacintucci , R. Cassano , T. Venturi , G. Macario , N. E. Kassim , W. Lane , G. Setti

Deep radio observations of the galaxy cluster Abell 781 have been carried out using the Giant Metrewave Radio Telescope at 325 MHz and have been compared to previous 610 MHz observations and to archival VLA 1.4 GHz data. The radio emission…

Cosmology and Nongalactic Astrophysics · Physics 2015-05-27 T. Venturi , S. Giacintucci , D. Dallacasa , G. Brunetti , R. Cassano , G. Macario , R. Athreya

Extended, steep-spectrum radio synchrotron sources are pre-dominantly found in massive galaxy clusters as opposed to groups. LOFAR Two-Metre Sky Survey images have revealed a diffuse, ultra-steep spectrum radio source in the low-mass…

Radio halos are extended and diffuse non-thermal radio sources present at the cluster center, not obviously associated with any individual galaxy. A strong correlation has been found between the cluster X-ray luminosity and the halo radio…

Cosmology and Nongalactic Astrophysics · Physics 2015-05-27 G. Giovannini , L. Feretti , M. Girardi , F. Govoni , M. Murgia , V. Vacca , J. Bagchi

New radio data at 330 MHz are presented for the rich clusters Abell 665 and Abell 2163, whose radio emission is characterized by the presence of a radio halo. These images allowed us to derive the spectral properties of the two clusters…

Astrophysics · Physics 2009-11-10 L. Feretti , E. Orru' , G. Brunetti , G. Giovannini , N. Kassim , G. Setti

Radio halos are megaparsec-scale diffuse, non-thermal radio sources located at the centers of galaxy clusters, tracing relativistic particles and magnetic fields in the intra-cluster medium. Their origin is generally attributed to cluster…

Context. Abell 1213, a low-richness galaxy system, is known to host an anomalous radio halo detected in data of the VLA. It is an outlier with regard to the relation between the radio halo power and the X-ray luminosity of the parent…

Cosmology and Nongalactic Astrophysics · Physics 2023-04-26 W. Boschin , M. Girardi , S. De Grandi , G. Riva , L. Feretti , G. Giovannini , F. Govoni , V. Vacca

Galaxy clusters with signs for a recent merger show in many cases extended diffuse radio features. This emission originates from relativistic electrons which suffer synchrotron losses due to the intra-cluster magnetic field. The mechanisms…

Astrophysics of Galaxies · Physics 2015-02-11 A. Drabent , M. Hoeft , R. F. Pizzo , A. Bonafede , R. J. van Weeren , U. Klein

Massive merging galaxy clusters often host diffuse Mpc-scale radio synchrotron emission. This emission originates from relativistic electrons in the ionized intracluster medium (ICM). An important question is how these synchrotron emitting…

Ultra-steep spectrum (USS) radio sources with complex filamentary morphologies are a poorly understood subclass of diffuse radio source found in galaxy clusters. They are characterised by power law spectra with spectral indices less than…

Recent advances in high-sensitivity radio observations have uncovered a population of faint, ultra-steep-spectrum sources in galaxy clusters, commonly known as radio phoenixes. However, their observational classification remains poorly…

Cosmology and Nongalactic Astrophysics · Physics 2025-10-28 Nasmi S Anand , Swarna Chatterjee , Ramij Raja , Majidul Rahaman , Abhirup Datta

We present the first detailed analysis of the ultra-steep spectrum radio halo in the merging galaxy cluster Abell 521, based on upgraded Giant Metrewave Radio telescope (uGMRT) observations. The combination of radio observations (300-850…

The knowledge of the origin and statistical properties of diffuse radio emission in galaxy clusters has appreciably improved thanks to the GMRT Radio Halo Survey, a project based on 610 MHz observations of clusters belonging to a…

Cosmology and Nongalactic Astrophysics · Physics 2011-02-10 Simona Giacintucci

Context: Hierarchical galaxy formation models indicate that during their lifetime galaxy clusters undergo several mergers. Here we report on the discovery of three diffuse radio sources in the periphery of Abell 2256, using the GMRT. Aims:…

Cosmology and Nongalactic Astrophysics · Physics 2015-05-14 R. J. van Weeren , H. T. Intema , J. B. R. Oonk , H. J. A. Rottgering , T. E. Clarke
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