Close-up view of a post-selected prestellar core at 500 μm (shown in Fig. A.1) illustrating the post-selection procedure. At each wavelength, the map colorscale is optimizedfor the immediate neighborhood of the core; the lowest and highest map values in the considered box are blanked by black and white colors, respectively. The source center position is marked by a cross, and the FWHM ellipse automatically derived by getsources is plotted.