Spectra of the observed transitions toward GO Tau and DM Tau. Intensity scale is ; conversion to flux density can be made by multiplying by 9 Jy/K. The thin red lines are the synthetic profiles obtained through the complete disk modeling (Sect. 4.5). The two groups of two hyperfine components for C₂H are presented in separate spectra: J = 7/2−5/2 in blue, J = 5/2−3/2 in green. The upper panels present, with a different intensity scale, the HCO⁺J = 3−2 spectra with the best-fit model superimposed.