Comparison between the predictions by Co³RaL and MORELI for the input model of M 2-9 (LTE, top) and CRL 618 (NLTE, bottom) presented in CSC17 that were designed to reproduce the IRAM-30 m single-dish data reported by these authors – see Sect. C. Left) Synthetic free-free continuum emission spectrum predicted by Co³RaL (black solid line) and MORELI (red dashed line). Data points (circles), shown as a reference, are as in Fig. 1 for M2-9 and as in CSC17 for CRL 618. Middle and Right) Synthetic H30α and H39α 1d spectra (integrated over the emitting region) predicted by Co³RaL (solid black histogram) and MORELI (dashed red histogram).