Derived spectral indices of the dust opacity for our sources as a function of uv-distance (bottom) or traced physical scales (top). The black lines represent the β = α−2 approximation, while the purple dots are derived as β = α−d log B(T)/d v in each bin. The orange line is a linear fit to the purple points. The green dashed line is the typical ISM β ∼ 1.6 value. Notes: (i) some sources display more bins than others due to differences in the signal-to-noise ratio of the detection; (ii) for IRAS4A we also report the measured β profile of Galametz et al. (2019) (dashed grey line and 1σ shaded region), limited within the scales that their data probed; and (iii) the profile for L1527 IRS is from Cacciapuoti et al. (2023).