Polarized Optical and Infrared Emission from High Redshift Radio Galaxies

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Abstract
We have detected highly polarized (> 5%) optical and/or infrared emission (rest frame UV to near infrared) from 5 of the 8 high redshift radio galaxies (HZRG; z > 0.7) we have observed. There are now a total of 9 (out of 12 observed) HZRG known to be polarized in spatially integrated measurements (cf.). We have made images of the extended polarized emission from two radio galaxies (3C 265 and 3C 256). Detection of extended polarized emission from a HZRG has previously been reported for 3C 368. All of the existing polarization observations support the hypothesis that the “alignment effect” (the tendency of the extended UV light to be aligned with the extended radio emission, e.g.) is not solely produced by a burst of star formation, but contains a very significant component produced by the scattering of the light from a hidden active galactic nucleus (AGN). Our modeling of the frequency dependence of the polarized flux from 3C 265 suggests that the most probable scatterer is dust.