CH₃CHO emission (in T_B scale) extracted at the MM1 position. The four panels show the frequency intervals where the CH₃CHO lines are located (see Table 1 for those unblended with other lines). The red line shows the synthetic spectrum which best reproduces the observations assuming LTE and optically thin emission obtained with the GILDAS−Weeds package (Maret et al. 2011) with source size = 03, T_rot = 87 K, N_CH3CHO = 2 × 10¹⁵ cm^-2, FWHM linewidth = 5.0 km s^-1, and LSR velocity = +1.7 km s^-1 (see footnote 2).