In the future, we will quantify the dependence of these uncertainties on the quality of high frequency observations available for a given source. We expect an overall error for each source which preserves the source's predicted spectrum of a factor of 1.5 for sources from the SGS catalog. They are based on an estimated spectral index uncertainty of 0.2 for sources with measured 2.7 GHz fluxes and of 0.5 for others. PMN sources with apparently rising spectra were set to flat spectra and assigned a spectral index uncertainty of 0.5 since radio spectra that rise from 2.7 to 5 GHz typically turn over and fall thereafter. For sources from the SGS catalog, we expect there to be an additional independent uncertainty at each frequency of a factor of 1.3 at frequencies below 150 GHz, a factor of 2 at frequencies between 150 and 300 GHz, and a factor of 3 at frequencies above 300 GHz.
All logarithms are base e.
Sources 2207 to 3977 are the brightest sources in the PMN catalog. We thank Aaron Sokasian for his assistance in compiling and analyzing the radio source measurements.