The observed polarization properties of an extended polarized radio source situated behind an irregular foreground Faraday screen are studied. Depolarization laws are derived for both a uniform and a linear source. The polarization behaviour is not strongly dependent on the assumed power spectrum of rotation measure (RM) fluctuations and generally behaves as a power law of wavelength when the root mean square rotated angle exceeds unity, a much slower fall off than given by Burn's formula. Polarization fluctuations are large, and the observation of patchy depolarization does not necessarily imply a clumpy foreground screen. The observed width of the RM distribution does depend on the assumed RM power spectrum. Internal and foreground depolarization have a similar wavelength dependence, and separating them will be difficult. Deductions of the screen properties from a Burn-type law are likely to be false. I estimate or constrain the properties of the depolarization screens in the Coma galaxy cluster and about quasars.
CITATION STYLE
Tribble, P. C. (1991). Depolarization of extended radio sources by a foreground Faraday screen. Monthly Notices of the Royal Astronomical Society, 250(4), 726–736. https://doi.org/10.1093/mnras/250.4.726
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