Maps of the first four principal components obtained by performing the PCA on the standardised data. The maps are constructed by summing for each pixel the contribution of each molecular transition scaled by the values reported in Table 2, i.e. they represent each pixel projected in the space of the principal components. The percentages represent the amount of correlation that can be reproduced by the single principal component. The blue, black, white, and grey diamonds indicate the dust, the HNCO, the c-C₃H₂, and the methanol peaks respectively.