ELECTRON AGING AND POLARIZATION IN TAILED RADIO GALAXIES

High-frequency observations of the tailed radio galaxies IC 310, NGC 1 265, 3C 129, and 3C 465 have been performed with the Effelsberg 100-m telescope. For the radio galaxies IC 310, NGC 1265 and 3C 465, radio d ata obtained at low frequencies with the Westerbork Synthesis Radio Te lescope are also available. These new radio data allow us to map the e xtended structure of the radio galaxies and obtain spectral and polari zation information in the outermost regions. The multi-frequency spect ra were used to study the synchrotron ageing of relativistic electrons with increasing distance from the active nucleus. We found that the s pectrum in each radio galaxy progressively steepens with distance, and at each location it is steeper at high frequencies. The spectra are f itted by models involving synchrotron energy losses and the critical f requency is obtained at increasing distance from the core. Assuming th at the magnetic field is the equipartition value, we obtain the radiat ing electron lifetimes and consequently their drift velocities. Our re sults imply the existence of reacceleration processes or bulk motions along the tails. The polarization data at 10.6 GHz give information on the intrinsic degree of polarized flux and the orientation of the mag netic field. We find that the polarization percentage increases along the tails, reflecting an increase of the degree of ordering of the mag netic field. The magnetic field in the tails is longitudinal.