Synchrotron spectra and ages of compact steep spectrum radio sources

The high-frequency integrated spectra of Compact Steep Spectrum (CSS) sourc es show breaks with a moderate spectral steepening well fitted by continuou s injection synchrotron spectra. In lobe-dominated CSS sources the radiativ e ages deduced by the synchrotron theory are in the range of up to 10(5) ye ars, if equipartition magnetic fields are assumed. These radiative ages are well correlated with the source size indicating that the CSS sources are y oung. In order to maintain the frustration scenario, in which the sources' lifetimes are approximate to 10(7) years, their equipartition magnetic fiel d would be systematically decreased by a factor greater than or similar to 20. To complete the sample used in this work, we conducted observations at 230 GHz with the IRAM 30-m telescope of those sources which did not have su ch high-frequency observations up to now.