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Science 3 November 2006:
Vol. 314. no. 5800, pp. 791 - 794
DOI: 10.1126/science.1131189
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Reports

Giant Ringlike Radio Structures Around Galaxy Cluster Abell 3376

Joydeep Bagchi,1* Florence Durret,2 Gastão B. Lima Neto,3 Surajit Paul4

In the current paradigm of cold dark matter cosmology, large-scale structures are assembling through hierarchical clustering of matter. In this process, an important role is played by megaparsec (Mpc)–scale cosmic shock waves, arising in gravity-driven supersonic flows of intergalactic matter onto dark matter–dominated collapsing structures such as pancakes, filaments, and clusters of galaxies. Here, we report Very Large Array telescope observations of giant (~2 Mpc by 1.6 Mpc), ring-shaped nonthermal radio-emitting structures, found at the outskirts of the rich cluster of galaxies Abell 3376. These structures may trace the elusive shock waves of cosmological large-scale matter flows, which are energetic enough to power them. These radio sources may also be the acceleration sites where magnetic shocks are possibly boosting cosmic-ray particles with energies of up to 1018 to 1019 electron volts.

1 The Inter-University Centre for Astronomy and Astrophysics (IUCAA), Post Bag 4, Ganeshkhind, Pune University Campus, Pune 411007, India.
2 Institut d'Astrophysique de Paris, UMR-7095, CNRS, Université Pierre et Marie Curie, Paris, France, and Observatoire de Paris-Meudon, LERMA, Paris, France.
3 Instituto de Astronomia, Geofísica e Ciências Atmosféricas, Universidade de São Paulo, São Paulo, Brazil 05508-900.
4 Institut fur Theoretische Physik und Astrophysik, Universität Würzburg, Sanderring 2, 97070 Würzburg, Germany.

* To whom correspondence should be addressed. E-mail: joydeep{at}iucaa.ernet.in

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Science. ISSN 0036-8075 (print), 1095-9203 (online)