The Spectra of the Strongest Non-Thermal Radio Sources in the Centimeter Wavelength Range.

Abstract

Flux densities and spectra of the strongest non-thermal radio sources are presented for frequencies up to 15 GHz. The spectra are mainly based on published absolute flux-density measurements. Thus these sources can be used as calibrators for observations in the centimeter-wavelength range. The flux densities are analyzed in a computer program that weighs the input data proportionally to the inverse square of the mean error. it is found that the Taurus A spectrum is best given by a straight line throughout the frequency range 400 MHz < < 35 GHz with a constant spectral index - 0.25 and a flux density of 974 f.u. (1 f.u. = 10-26 W Hz-1) at 1 GHz. The Cassiopeia A spectrum is best approximated by two straight lines, a low-frequency part with spectral index -0.74 and flux density of 3110 f.u. at 1 GHz, and a high-frequency part with spectral index -1.18 and a flux density of 495 f.u. at 10 GHz. The change in the spectral index occurs at about 7 GHz. For the Cygnus A spectrum two straight lines give the best fit, the change in the spectral index occurring at 1.6 GHz. The Virgo A spectrum is best fitted by a straight line.