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Galaxy clusters grow by a sequence of mergers with other clusters and galaxy groups. During these mergers, shocks and/or turbulence are created within the intracluster medium (ICM). In this process, particles could be accelerated to highly…

Cosmology and Nongalactic Astrophysics · Physics 2015-05-27 R. J. van Weeren , H. J. A. Rottgering , M. Bruggen

Radio halos and relics are Mpc-scale diffuse radio sources in galaxy clusters, with a steep spectral index $\alpha>1$ ($S\propto \nu^{-\alpha}$). It has been proposed that they arise from particle acceleration induced by turbulence and weak…

We present the first band-2 (120--250\,MHz) uGMRT (upgraded Giant Metrewave Radio Telescope) observations of the bimodal galaxy cluster Abell\,1644 (\(z = 0.0471\)), complemented by Chandra X-ray data. While weak lensing measurements reveal…

Astrophysics of Galaxies · Physics 2025-12-24 Humaira Bashir , R. Kale , Asif Iqbal , Manzoor A. Malik

The remnant radio galaxies in galaxy clusters are important sources of seed relativistic electron population in the intra-cluster medium (ICM). Their occurrence and spectral properties are poorly studied. In this work we present a broadband…

Astrophysics of Galaxies · Physics 2018-08-22 Ruta Kale , Viral Parekh , K. S. Dwarakanath

We report extensive VLA and ATCA observations of the two diffuse radio sources in the cluster of galaxies Abell 548b, which confirm their classification as relics. The two relics (named A and B) show similar flux density, extent, shape,…

Astrophysics · Physics 2009-11-11 L. Feretti , M. Bacchi , O. B. Slee , G. Giovannini , F. Govoni , H. Andernach , G. Tsarevsky

In this paper we present Very Large Array (VLA) 1.4 GHz (21 cm) observations of the region between the centres of A3558 and A3562, in the majorcluster merger complex of the Shapley Concentration. Our final catalogue includes a total of 174…

Astrophysics · Physics 2009-11-10 S. Giacintucci , T. Venturi , S. Bardelli , D. Dallacasa , E. Zucca

We present the results of a 22 cm radio survey carried out with the A3558 complex, a chain formed by the merging ACO clusters A3556-A3558-A3562 and thetwo groups SC1327-312 and SC1323-313, located in the central region of the complex, a…

Astrophysics · Physics 2009-10-31 T. Venturi , S. Bardelli , R. Morganti , R. W. Hunstead

The ASKAP-EMU survey is a deep wide-field radio continuum survey designed to cover the entire southern sky and a significant fraction of the northern sky up to $+30^{\circ}$. Here, we report a discovery of a radio relic in the merging…

Low-frequency radio observations of galaxy clusters are the key to detecting the diffuse extended emission associated with them. The presence and properties of such radio sources in galaxy clusters reveal the existence of magnetic fields on…

Astrophysics · Physics 2009-11-13 R. F. Pizzo , A. G. de Bruyn , L. Feretti , F. Govoni

Here we analyze radio, optical, and X-ray data for a peculiar cluster Abell 578. This cluster is not fully relaxed and consists of two merging sub-systems. The brightest cluster galaxy, CGPG 0719.8+6704, is a pair of interacting ellipticals…

High Energy Astrophysical Phenomena · Physics 2015-06-03 K. Hagino , L. Stawarz , A. Siemiginowska , C. C. Cheung , D. Koziel-Wierzbowska , A. Szostek , G. Madejski , D. E. Harris , A. Simionescu , T. Takahashi

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…

Abell 2744, also known as Pandora's Cluster, is a complex merging galaxy cluster. While a major merger is clear along the north-south axis, the dynamical state of the northwest subcluster has been highly uncertain. We present ultra-deep…

Cosmology and Nongalactic Astrophysics · Physics 2024-07-04 Urmila Chadayammuri , Ákos Bogdán , Gerrit Schellenberger , John ZuHone

Recent low-frequency radio observations at 140 MHz discovered a 3 Mpc-long bridge of diffuse emission connecting the galaxy clusters Abell 0399 and Abell 0401. We present follow-up observations at 60 MHz to constrain the spectral index of…

We present new XMM-Newton observations of the northwest (NW) radio relic region in the cluster Abell 3667. We detect a jump in the X-ray surface brightness and X-ray temperature at the sharp outer edge of the radio relic which indicate that…

Cosmology and Nongalactic Astrophysics · Physics 2015-06-12 Craig L. Sarazin , Alexis Finoguenov , Daniel R. Wik

We report on a spectral study at radio frequencies of the giant radio halo in A2142 (z=0.0909), which we performed to explore its nature and origin. A2142 is not a major merger and the presence of a giant radio halo is somewhat surprising.…

Cosmology and Nongalactic Astrophysics · Physics 2017-07-26 T. Venturi , M. Rossetti , G. Brunetti , D. Farnsworth , F. Gastaldello , S. Giacintucci , D. V. Lal , L. Rudnick , T. W. Shimwell , D. Eckert , S. Molendi , M. Owers

Context. Radio halos are megaparsec-scale diffuse radio sources{ mostly} located at the centres of merging galaxy clusters. The common mechanism invoked to explain their origin is the re-acceleration of relativistic particles caused by…

Cosmology and Nongalactic Astrophysics · Physics 2021-10-27 G. Di Gennaro , R. J. van Weeren , R. Cassano , G. Brunetti , M. Brüggen , M. Hoeft , E. Osinga , A. Botteon , V. Cuciti , F. de Gasperin , H. J. A. Röttgering , C. Tasse

Radio continuum emission at 1.4 GHz was used to identify active galaxies in a sample of 20 nearby Abell clusters. The radio emission indicates either an active galactic nucleus or current star formation, and optical spectroscopy was used to…

Astrophysics · Physics 2007-05-23 Neal A. Miller

Giant radio haloes are diffuse synchrotron sources typically found in merging galaxy clusters, while smaller mini-haloes occur in cool-core clusters. Both trace cosmic-ray electrons in the intracluster medium, though recent observations…

We report on a Suzaku measurement of the shock feature associated with the western radio relic in the merging cluster A3376. The temperature profile is characterized by an almost flat radial shape with kT ~ 4 keV within 0.5 r200 and a rise…

Cosmology and Nongalactic Astrophysics · Physics 2015-06-03 Hiroki Akamatsu , Motokazu Takizawa , Kazuhiro Nakazawa , Yasushi Fukazawa , Yoshitaka Ishisaki , Takaya Ohashi