K-band polarimetry of seven high-redshift radio galaxies

We present the results of K-band imaging polarimetry of seven 3CR radio galaxies with 0.7 < z < 1.2. We find strong evidence for polarization in three sources: 3C 22, 3C 41 and 3C 114. Of these, 3C 41 shows strong evidence of having a quasar core the infrared light of which is scattered by dust. We also find some evidence for polarization in 3C 54 and in 3C 356. The two point-like sources (3C 22 and 3C 41) and the barely-elongated 3C 54 appear to have of order 10 per cent of their K-band flux contributed by scattered light from the active nucleus. We conclude that scattered nuclear light can form a significant component of the near-infrared light emitted by high-redshift radio galaxies, and discuss models in which the scattering particles are electrons and dust grains.