SIMBAD references

We present a spectral aging study of a sample of 5 giant radio galaxies based on radio continuum data obtained at frequencies between 326MHz and 10.6GHz. Using synchrotron loss models, we determined injection spectral indices and particle ages where possible. The results suggest ages not older than 4.10⁷yr, a value that is typical for radio galaxies with ``normal'' sizes. From equilibrium considerations between lobes and jets on the one hand and the ambient medium on the other we derived estimates of the density of the intergalactic medium, with average values in the range of a few 10^–5cm^–3.