In a sample of high-luminosity 3C radio sources, a strong correlation between spectral index and depolarization has been found: the lobe which is less depolarized has the flatter spectrum in 12 out of 13 cases. We compare this result with that of Garrington et al. and Laing, who found that the less-depolarized lobe is associated with the presence of a jet on the same side of the nucleus. No obvious physical mechanism seems to account naturally for both phenomena.
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Ronghui Liu, Guy Pooley. Spectral index and depolarization asymmetry in powerful radio sources, Monthly Notices of the Royal Astronomical Society, 1991, 343-351, DOI: 10.1093/mnras/249.2.343