Asymmetric depolarization in double low-luminosity radio galaxies

To investigate the presence of the Laing-Garrington effect (i.e. the lobe containing the jet more depolarized than that containing the counter-jet), we analyse polarization data at 6 and 20 cm for a sample of double low-luminosity radio galaxies. The effect is well visible, although not very strong. We therefore confirm what was inferred in a previous paper based on data at one frequency (20 cm) only. Furthermore, we find that radio galaxies with strong radio cores show a more pronounced asymmetry in depolarization. We conclude that the presence of the Laing-Garrington effect in our sample is a indication that relativistic motions do occur on the kpc scale of low-luminosity radio galaxies as recently suggested by theoretical arguments and observational evidence.