LAMBDA Graphics: CMB and Radio Monopole Spectrum
Spectrum of the extragalactic monopole from selected studies. The datasets used are indicated in the legend and the plotted data and references are given in this table. Different methods of Galactic foreground removal were used by different authors, and here a contribution from unresolved known extragalactic source populations has not been subtracted. (For a more comprehensive compilation of monopole data, see Baiesi et al. 2020). The microwave results are consistent with a blackbody spectrum with CMB temperature 2.72548 +- 0.00057 K (Fixsen 2009). The origin of the radio background has not been established. It is much stronger than expected from known populations of extragalactic sources and its spectrum is consistent with a single power law of index -2.58 (Dowell and Taylor 2018).
The extragalactic monopole spectrum above 0.5 GHz on a log-linear scale. The CMB temperature of 2.72548 K is shown by the gray line.