Optical depth spectra toward the ALMA continuum intensity peak of the sources. The red line shows the best fit for each spectrum, and the black line shows the optical depth spectrum. The R² of the fits is shown in the lower right corners. Left panels: Gaussian fits of ¹³CO₂, OCN⁻, CO, and OCS. Right panels: colored lines show the components of the laboratory spectra of H₂CO:H₂O (blue), H₂O (green), NH﹩{}_{4}^{+}﹩ (15 K, purple), H₂O:CO:CO₂ (orange), and NH﹩{}_{4}^{+}﹩(120 K, cyan).