FWHM values of the observed (gray-shaded region) and simulated (symbols) rotational lines of ¹³CO and C¹⁸O as indicated in a 20″ beam. The observed values are taken from Jørgensen et al. (2002), van Kempen et al. (2009a), and San Jose-Garcia et al. (2013). The FWHM of synthetic lines are indicated at specific inclinations as indicated by the symbols: circles for 0°, triangles for 45°, and squares for 90°. The comparison of the FWZI values are specifically for the C¹⁸O 3–2 line. The different colors represent the different types of simulations: 3D RSD (RSD), 3D pseudo-disk (no RSD), and 2D semi-analytical model (2D Model).