Dust and synchrotron B-mode power versus multipole. The dust power at 95 and 150 GHz, and that of synchrotron at 95 GHz are compared with CMB B modes from primordial gravitational waves (grey lines) for three values of the tensor-to-scalar ratio, r = 0.1, 0.01, and 0.001, and from lensing (blue line) for the Planck 2015 ΛCDM model (Planck Collaboration XIII 2016). The coloured bands show the range of power measured from the smallest (LR24) to the largest (LR71) sky regions in our analysis. The lower limit of the synchrotron band is derived from the S-PASS data analysis in Krachmalnicoff et al. (2018).