Maps of the spectral index in the 15 ALMA-IMF fields. We chose the colours such that red traces dust thermal emission, blue traces free-free emission, and green likely traces a mixture of dust and free-free emissions. The maps display the spectral index value only where the 3 mm intensity exceeds 3 σ. The black ellipses display the sources extracted by getsf. We show the remaining fields in Fig. B.1.