353 × 545 cross-power spectrum in the GASS field (using Mask1). The black line is the cross-power spectrum of the dust model, with error bars not shown for clarity. The red points are the result of a power-law fit to the dust model, using the bins of the CIB power spectrum. The CIB obtained by the spatial removal of the dust is shown in orange (note that it stops at ℓ ≃ 1000 due to the angular resolution of the Hi data), while the CIB obtained from the spectral removal of the dust (i.e., on the power spectrum) is shown in light blue (diamonds). We see that the two methods give identical CIB for ℓ ≳ 300. In dark blue is the cross-power spectrum of the CMB-free frequency maps; the dust removal is negligible for ℓ ≥ 700. For clarity the points have been shifted by ℓ ± 3% and the error linked to the cirrus bias (see Sect. 3.2.2) have not been added.