Synchrotron spectra and ages of compact steep spectrum radio sources

The high-frequency integrated spectra of Compact Steep Spectrum (CSS) sources show breaks with a moderate spectral steepening well fitted by continuous injection syn- chrotron spectra. In lobe-dominated CSS sources the radiative ages deduced by the synchrotron theory are in the range of up to 10 5 years, if equipartition magnetic fields are assumed. These radiative ages are well correlated with the source size indicat- ing that the CSS sources are young . In order to maintain the frustration scenario, in which the sources' lifetimes are 10 7 years, their equipartition magnetic field would be systemati- cally decreased by a factor > 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 such high-frequency observations up to now.