(a) Source-subtracted Ka (30 GHz) and Ku-band (14.5 GHz) data plotted to equal brightness temperature scale. Both represent sky amplitudes, convolved with the double-switched beam pattern of the RING5M observations, indicated at the bottom left of the figure. Approximately half of the RING5M fields show CMB-like signals (equal brightness temperature at both frequencies), while the other half show temperature signals with a steep spectral dependence. (b) The likelihood of the spectral index of the RING5M data, assuming that a single process is responsible for the signals at both frequencies. Clearly pure CMB () is ruled out with high significance.
