Line main characteristics: S/Ns, opacities, ratios of the volume density to the effective critical densities, and ratios of the excitation and kinetic temperatures. The blue and red curves show the results for the (1 − 0) and (2 − 1) lines, respectively. The values of the parameters that are fixed when generating the RADEX spectra are listed in the bottom row, except for the abundances that are given in Eq. (16).