Comparison between line profiles. Left: line profile for H¹³CN (1 → 0) as given by RADMC-3D. Middle: line profile for the same setup than left panel, but setting the hydrogen density near to zero, and therefore corresponding to the background contribution. Right: resulting line profile when we substract the background (middle plot) to the RADMC-3D profile (left plot). Line profiles like the one on the right are those that we used for the analysis of H¹³CN (1 → 0) and H¹³CO⁺ (1 → 0).