Sinusoidal-type patterns in single-spaxel spectra extracted from the emsm data cube with a spaxel size of 0.1″. Top panel: LBQS 0302−0019 spectrum integrated over an aperture of r = 0.5″ (orange curve), in comparison with the spectrum of the brightest spaxel (blue curve). Both spectra are normalised to their maximum values for visualisation purposes. The wiggles affecting the single-spaxel spectrum are reported in grey and are obtained as the difference between the blue and orange curves (see Fig. 5 for details). Bottom panel: Wiggles obtained from the eight pixels closest to the brightest one.