Astronomy and Astrophysics – Astrophysics – Cosmology and Extragalactic Astrophysics
Scientific paper
2010-02-02
Astronomy and Astrophysics
Astrophysics
Cosmology and Extragalactic Astrophysics
23 pages, 21 figures. Higher resolution available at http://www.ira.inaf.it/~bonafede/paper.pdf. A&A accepted
Scientific paper
The aim of the present work is to constrain the Coma cluster magnetic field strength, its radial profile and power spectrum by comparing Faraday Rotation Measure (RM) images with numerical simulations of the magnetic field. We have analyzed polarization data for seven radio sources in the Coma cluster field observed with the Very Large Array at 3.6, 6 and 20 cm, and derived Faraday Rotation Measures with kiloparsec scale resolution. Random three dimensional magnetic field models have been simulated for various values of the central intensity B_0 and radial power-law slope eta, where eta indicates how the field scales with respect to the gas density profile. We derive the central magnetic field strength, and radial profile values that best reproduce the RM observations. We find that the magnetic field power spectrum is well represented by a Kolmogorov power spectrum with minimum scale ~ 2 kpc and maximum scale ~ 34 kpc. The central magnetic field strength and radial slope are constrained to be in the range (B_0=3.9 microG; eta=0.4) and (B_0=5.4 microG; eta=0.7) within 1sigma. The best agreement between observations and simulations is achieved for B_0=4.7 microG; eta=0.5. Values of B_0>7 microG and <3 microG as well as eta < 0.2 and eta > 1.0 are incompatible with RM data at 99 % confidence level.
Bonafede Annalisa
Dallacasa Daniele
Dolag Klaus
Feretti Luigina
Giovannini Gabriele
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