Spectra of the observational (in blue) and simulated (in red) data extracted from the position of different cores and molecular centers for the vibrationally excited transition CH₃ CN ν₈ = 1, J = 12−11, K = 1 − (−1). The spectra are arranged according to the position of the corresponding cores and molecular centers along a south–north direction, starting from the most southern core. The name of the core and molecular center is shown for each panel. The continuum correction necessary to match the continuum level of the observation and simulation is indicated in the top right corner of each panel.