Correlated fluxes (F_cor, left ordinate) or visibilities (, right ordinate) of the Circinus galaxy at 12 μm as a function of the projected baseline length BL (bottom axis) or spatial frequency (top axis). The data are colour-coded with the position angle (see compass on the top right). Overplotted by two thick continuous lines are the correlated fluxes of the three-component model discussed in Sect. 4. The correlated fluxes of the model are along (violet) and (dark blue). Note that the errors in the measurements with UT baselines (BL > 30 m) are smaller than the plot symbol and that the model does not fully reproduce the total flux (plotted at BL = 0 m) for λ > 11.5 μm (see Sect. 5.3).