Double relics in Abell 2345 and Abell 1240

Free access article

Issue		A&A Volume 494, Number 2, February I 2009


Page(s)		429 - 442
Section		Cosmology (including clusters of galaxies)
DOI		http://dx.doi.org/10.1051/0004-6361:200810588
Published online		20 November 2008

A&A 494, 429-442 (2009)
DOI: 10.1051/0004-6361:200810588

Spectral index and polarization analysis

A. Bonafede^{1, 2}, G. Giovannini^{1, 2}, L. Feretti², F. Govoni³, and M. Murgia^{2, 3}

¹ Universitá di Bologna, Dip. di Astronomia, via Ranzani 1, 40126 Bologna, Italy
e-mail: bonafede@ira.inaf.it
² INAF, Istituto di Radioastronomia, via Gobetti 101, 40129 Bologna, Italy
³ INAF – Osservatorio Astronomico di Cagliari, Strada 54, Loc. Poggio dei Pini, 09012 Capoterra (Ca), Italy

Received 14 July 2008 / Accepted 19 September 2008

Abstract
Aims. The aim of the present work is to study the radio properties of double relics in Abell 1240 and Abell 2345 in the framework of double relic formation models.
Methods. We present new Very Large Array observations at 20 and 90 cm for these two clusters. We performed spectral index and polarization analysis and compared our results with expectations from theoretical models.
Results. The presence of double relics in these two cluster is confirmed by these new observations. Double relics in Abell 1240 show radio morphology, spectral index, and polarization values in agreement with “outgoing merger shocks” models. One of the relics of Abell 2345 shows a peculiar morphology and spectral index profile, which are difficult to reconcile with present scenarios. We suggest a possible origin for this peculiar relic.

Key words: galaxies: clusters: general -- galaxies: clusters: individual: Abell 1240 -- galaxies: clusters: individual: Abell 2345 -- radiation mechanisms: non-thermal -- polarization -- magnetic fields

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