The intracluster magnetic field power spectrum in Abell 2382

¹ INAF - Istituto di Radioastronomia, via Gobetti 101, 40129 Bologna, Italy e-mail: guidet_s@ira.inaf.it
² INAF - Osservatorio Astronomico di Cagliari, Loc. Poggio dei Pini, Strada 54, 09012 Capoterra (CA), Italy
³ Dipartimento di Fisica, Univ. Bologna, via Irnerio 46, 40126 Bologna, Italy
⁴ INAF - Osservatorio Astronomico di Bologna, via Ranzani 1, 40127 Bologna, Italy
⁵ Stanford Univ./SLAC, 2575 Sand Hill Road, Menlo Park, CA 94025, USA

Received: 30 August 2007
Accepted: 4 November 2007

Abstract

Aims. The goal of this work is to put constraints on the strength and structure of the magnetic field in the cluster of galaxies A2382. We investigate the relationship between magnetic field and Faraday rotation effects in the cluster, using numerical simulations as a reference for the observed polarization properties.

Methods. For this purpose we present Very Large Array observations at 20 cm and 6 cm for two polarized radio sources embedded in A2382, and we obtained detailed rotation measure images for both of them. We simulated random three-dimensional magnetic field models with different power spectra and thus produced synthetic rotation measure images. By comparing our simulations with the observed polarization properties of the radio sources, we can determine the strength and the power spectrum of intra-cluster magnetic field fluctuations that reproduce the observations best.

Results. The data are consistent with a power-law magnetic-field power spectrum with the Kolmogorov index , while the outer scale of the magnetic field fluctuations is close to 35 kpc. The average magnetic field strength at the cluster centre is about 3 μG and decreases in the external region as the square root of the electron gas density. The average magnetic field strength in the central 1 Mpc³ is about 1 μG.