Top: probability density function of the distribution of fluxes within the data cube and the associated Gaussian fit (red dashed curve). The value ϕ corresponds to the flux of each pixel (in the 3D data cube), and the spatial variation of the noise has not been corrected at this stage. Bottom: residues associated with the distribution and its Gaussian fit. We observe that the distribution is not Gaussian, which we expect from a cube containing a signal. The residues are mostly symmetrical, showing that the signal is very faint and needs advanced detection methods.