Spectra of the vibrationally excited transition ν₈ = 1, J = 12−11, K = 1 − (−1) taken from the center of different cores. The blue solid line shows the observational data, while the red solid lines show the simulated data when the gas temperature equals the dust temperature. The bottom panels also show the simulated spectra after modifying the gas temperature by 50 K (green) and 150 GHz (yellow), as discussed in Sect. 6.3. The continuum correction necessary to match the continuum level of the observation and simulation is indicated in the top right corner of each panel.