Intensity profiles on logarithmic scales at 1.3 and 3 mm expressed in brightness temperature, calculated using the full Planck function. The shaded area corresponds to the uncertainty in the mean (Section 4.3). The 1.3–3 mm spectral index α calculated from the profiles is shown in magenta with the corresponding value in the right y-axis. The magenta shaded area shows the uncertainty calculated propagating the errors in the intensity profiles. The vertical dotted line represents the geometric mean of the beam size, indicating that emission beyond this point is spatially well resolved.