C¹⁸0 (1−0) and (2−1) spectra along the main cut. The blue spectra show the observational data including the archival J=1−0 spectra from Tafalla et al. (2004) and our J=2−1 spectra. The black spectra show the modeled J=2−1 spectra from Fig. B.1. The red spectra show the modeled spectra of the asymmetric onion-like model embedded in an envelope that is a layer with A_V =3 mag. Each column corresponds to different offsets from the center of L 1498. The green dashed lines indicate the 3σ noise level.