title: Giant ringlike radio structures around galaxy cluster Abell 3376.
abstract: 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 ( approximately 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 10(18) to 10(19) electron volts.
authors.affiliation: Inter-University Centre for Astronomy and Astrophysics (IUCAA), Post Bag 4, Ganeshkhind, Pune University Campus, Pune 411007, India. joydeep@iucaa.ernet.in
authors.forename: Joydeep
authors.initials: J
authors.lastname: Bagchi
authors.forename: Florence
authors.initials: F
authors.lastname: Durret
authors.forename: Gastão B Lima
authors.initials: GB
authors.lastname: Neto
authors.forename: Surajit
authors.initials: S
authors.lastname: Paul