Observations of Cygnus A at 15 GHz with the 5-km radio telescope

The compact 'head' regions in the components of Cygnus A have been mapped out with the 5-km telescope at 15.4 GHz, the resolution being 0'.65 arc in right ascension and 1'.0 arc in declination. The maps reveal, as had been inferred from preliminary 15 GHz observations with the 5-km telescope, that the 'head' in the Sf component has a sharply truncated leading edge. A comparison of the present data with those previously obtained at 5 GHz shows that the 'head' regions have spectral indices significantly lower than those of the lower brightness 'tails'. Improved estimates have been obtained of the physical conditions within the various regions of the source. (author)