APS amplitude as a function of frequency for the continuum (solid black line), the [C_II] generated with the DL14 or L18 SFR-L_[CII] relations (green and light green lines, respectively), the residual continuum obtained with PCA (Sect. 3.1) using the first two principal components (orange line), and the residual continuum obtained with arPLS (Sect. 3.2, blue line). The power spectrum amplitude is averaged at k = 0.26 arcmin⁻¹ in frequency channels of 1 GHz width.