Upper limits on K-band polarization in three high-redshift radio galaxies:53W091, 3C 441 and MRC 0156-252

We present the results of K-band imaging polarimetry of three radio galaxie s, including the very red and apparently old z = 1.55 galaxy 53W091. We fin d weak evidence for polarization in components of 3C 441 and in the south-e astern companion of 53W091, but no evidence of significant polarization in 53W091 itself. We also find strong evidence that MRC 0156-252 is unpolarize d. We present upper limits for the K-band polarization of all three sources . For 53W091, the lack of significant K-band polarization provides further confidence that its red R-K colour can be attributed to a mature stellar po pulation, consistent with the detailed analyses of its ultraviolet spectral -energy distribution which indicate a minimum age of 2-3.5 Gyr.