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Lookup NU author(s): Dr Andrew Fletcher, Professor Anvar ShukurovORCiD
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We employ an analytical model that incorporates both wavelength-dependent and wavelength independent depolarization to describe radio polarimetric observations of polarization at lambda lambda lambda 3.5, 6.2, 20.5 cm in M51 (NGC 5194). The aim is to constrain both the regular and turbulent magnetic field strengths in the disk and halo, modeled as a two- or three-layer magneto-ionic medium, via differential Faraday rotation and internal Faraday dispersion, along with wavelength independent depolarization arising from turbulent magnetic fields, A reduced chi-squared analysis is used for the statistical comparison of predicted to observed polarization maps to determine the best-fit magnetic field configuration at each of four radial rings spanning 2.4-7.2 kpc in 1.2 kpc increments. We find that a two layer modeling approach provides a better fit to the observations than a three layer model, where the near and far sides of the halo are taken to be identical, although the resulting hest-fit magnetic field strengths are comparable, This implies that all of the signal from the far halo is depolarized at these wavelengths. We find a total magnetic field in the disk of approximately 18 mu G and a total magnetic field strength in the halo of similar to 4-6 mu G Both turbulent and regular magnetic field strengths in the disk exceed those in the halo by a factor of a few. About half of the turbulent magnetic field in the disk is anisotropie, but in the halo all turbulence is only isotropic,
Author(s): Shneider C, Haverkorn M, Fletcher A, Shukurov A
Publication type: Article
Publication status: Published
Journal: Astronomy & Astrophysics
Year: 2014
Volume: 568
Online publication date: 22/08/2014
Acceptance date: 18/06/2014
ISSN (print): 0004-6361
ISSN (electronic): 1432-0746
Publisher: EDP Sciences
URL: http://dx.doi.org/10.1051/0004-6361/201424192
DOI: 10.1051/0004-6361/201424192
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