Frequency dependence of the amplitude A^BB of the angular power spectrum computed on M_B2 defined in Sect. 6.1, normalized to the 353 GHz amplitude (red points); amplitudes for cross-power spectra are plotted at the geometric mean frequency. The square of the adopted dust SED, a modified blackbody spectrum with β_d = 1.59 and T_d = 19.6 K, is overplotted as a black dashed line, again normalized to the 353 GHz point. The ± 1σ error area arising from the expected dispersion of β_d, 0.11 for the M_B2 patch size (Sect. 2.2.1), is shown in light grey.