Application of the method described in Sect. 3.4 to source 2 of region A. Left: ¹³CO and C¹⁸O spectra convolved with a 1D box of 5 pixels (continuous red and green lines), the Gaussian fit of the ¹³CO to correct forthe self-absorption (dashed blue line), and the C¹⁸O spectrum scaled to the peak of the ¹³CO Gaussian fit (dashed-point magenta line). Right: Gaussian fit to the scaled C¹⁸O spectrum (dashed-point blue line), ¹³CO residual (dashed black line) resulting from the subtraction of the scaled C¹⁸O Gaussian from the ¹³CO Gaussian, and the blue and red wings (green line).