Spectral index maps (α, with S_ν ∝ ν^α) derived from the continuum emissions at ν = 344.5 GHz and 694 GHz (α₁: left panel), and from ν = 229.7 GHz and 344.5 GHz (α₂: middle panel). Contours span the range α = [ − 3, 3] in steps of 1. The common aperture adopted to derive the spectral index map is (red circle). The SED of continuum emission from 229.7 GHz to 694 GHz for the E-knot, the C-knot and the combined S1+S2 region are shown in the right panel.