Cuts of the brightness temperature distribution along the east-west axis for real and synthetic observations at four wavelengths. The black solid line in each panel represents the ALMA and VLA observations shown in Fig. 1. The colored lines indicate models with different maximum dust grain sizes, taking values of a_max = 10, 100, and 1000 µm. We include models accounting for the sublimation of 80% of the carbonaceous material in the form of refractory organics. The sublimation zone extends over a 10 au radius where the gas temperature exceeds 300 K. The black line under every wavelength label indicates the angular resolution.