Observed chemical structure of L1544

We classified our sample in five families, depending on the location of their emission peaks within the core. Furthermore, to systematically study the correlations among different molecules, we have performed the principal component analysis (PCA) on the integrated emission maps.

The PCA allows us to reduce the amount of variables in our dataset. Finally, we compare the maps of the first three principal components with the H_2_ column density map, and the T_dust_ map of the core. The results of our qualitative analysis is the classification of the molecules in our dataset in the following groups: (i) the c-C_3_H_2_ family (carbon chain molecules like C_3_H and CCS), (ii) the dust peak family (nitrogen-bearing species like N_2_H^+^ ), (iii) the methanol peak family (oxygen-bearing molecules like methanol, SO and SO_2_, (iv) the HNCO peak family (HNCO, propyne and its deuterated isotopologues).