Correlation between the temperature as measured by CH₃CN and CH₃CCH. All the other combinations between the tracers analysed are included in the online material in Fig. A. The best fit is shown as a blue solid line. The uncertainties due to the line parameters are indicated by the shaded region – dark- and light yellow for 68% and 95% HPD intervals, respectively. The intrinsic scatter in the relation is indicated by the dashed black lines. At the bottom right of the panels the Spearman correlation coefficient is indicated.