Radiative ages in a representative sample of low luminosity radio galaxies

Two frequency observations, mainly at 1.4 and 5 GHz from the VLA, have been used to study spectral variations along the lobes of some nearby low lumin osity radio galaxies that constitute a representative sample selected from the B2 catalogue. The variations of the spectral index have been interprete d as being due to synchrotron and inverse Compton losses and characteristic spectral ages are deduced for the relativistic electrons. The radiative ag es are in the range of several 10(7) years. These ages correlate well with the source sizes. They also appear to be consistent with dynamical ages det ermined from ram-pressure arguments, if we make reasonable assumptions abou t the ambient gas density and allow for very moderate deviations from the e quipartition conditions. There appears to be a significant difference betwe en the radiative ages of sources in our sample and those of more powerful 3 CR radio sources. We briefly discuss the possibility of re-acceleration pro cesses and indicate some objects where these may occur.