Determining the shape of spectra in extended radio sources

Abstract

An innovative technique for determining the shape of the synchrotron spectra in extended radio sources is presented. The method involves the use of a three-frequency 'color-color' diagram that emphasizes differences in the shapes of various theoretical models. The technique was applied to multifrequency data of Cygnus A and a single spectral shape was found which appears to fit all positions in the source. The shape differs from standard models and there is no evidence that the spectrum is a power law in any frequency range. Results obtained do not indicate that postinjection relativistic particle acceleration occurs in this source. This study calls into question the nature of injected electron energy distribution and the validity of all current spectral analyses.