Spectral index map from the ALMA continuum measurements from 211 GHz to 275 GHz (see Sect. 4.1) for Sgr B2(N) (left panel) and Sgr B2(M) (right panel). The ALMA 1.3 mm (242 GHz) continuum emission, as shown in Figs. 4 and 5, is orvelaid in gray contours. The synthesized beam is and is shown in the bottom right corner of each panel. The continuum sources listed in Tables 1 and 2 are indicated with crosses and numbers.