Panel a: velocity-integrated [CII] map of VC_9780 (#A) and panel b: C15_705574 (#B), obtained by collapsing channels (velocity ranges in the upper-left corners) of line-emission in 1″-aperture spectra (see Sect. 3.3) centred on the rest-frame UV centroids of #A and #B (indicated with a black plus symbol). Black solid (dashed) contours indicate the positive (negative) significance levels at [2, 4, 8]σ of [CII] flux, where σ_[CII] = 50 mJy km s⁻¹ beam⁻¹ in panel a and σ_[CII] = 57 mJy km s⁻¹ beam⁻¹ in panel b. The white contours indicate the positive significance levels at [3, 4]σ of FIR-continuum emission, where σ_cont = 59 μJy beam⁻¹. No negative contours at the same significance levels were found. The dashed blue ellipses indicate the beam-convolved FWHM_x × FWHM_y regions obtained by 2D Gaussian models, and correspond to the apertures used to extract the final [CII] spectra of #A and #B (see Sect. 3.3), shown in Fig. 4. The ALMA beam sizes are given in the bottom-left corners. North is up and east is to the left.