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Issue A&A
Volume 378, Number 3, November II 2001
Page(s) 777 - 786
Section Extragalactic astronomy
DOI http://dx.doi.org/10.1051/0004-6361:20011219



A&A 378, 777-786 (2001)
DOI: 10.1051/0004-6361:20011219

Correlation of the magnetic field and the intra-cluster gas density in galaxy clusters

K. Dolag1, S. Schindler2, F. Govoni3, 4 and L. Feretti4

1  Max-Planck-Institut für Astrophysik, PO Box 1317, 85741 Garching, Germany
2  Astrophysics Research Institute, Liverpool John Moores University, Twelve Quays House, Birkenhead CH41 1LD, UK
3  Dipartimento di Astronomia, Univ. Bologna, Via Ranzani 1, 40127 Bologna, Italy
4  Istituto di Radioastronomia CNR, Via P. Gobetti, 101 40129 Bologna, Italy

(Received 1 August 2001 / Accepted 28 August 2001 )

Abstract
We present a correlation between X-ray surface brightness and Faraday rotation measure in galaxy clusters, both, from radio and X-ray observations as well as from modeling of the intra-cluster medium. The observed correlation rules out a magnetic field of constant strength throughout the cluster. Cosmological, magneto-hydrodynamic simulations of galaxy clusters are used to show that for a magnetic field of cosmic origin this correlation is expected and excellently reproduces the observations showing that the rms scatter of the Faraday rotation increases linearly with the X-ray surface brightness. From the correlation between the observable quantities, rotation measure and X-ray surface brightness, we infer a relation between the physical quantities: magnetic field and gas density. For the best available observations, those of A119, we find $B \propto n_{\rm e}^{0.9}$.


Key words: magnetic fields -- galaxies: clusters: general

Offprint request: K. Dolag, kdolag@mpa-garching.mpg.de

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