Black dots: total flux measured by single-dish telescopes (VISIR/PAH2 and T-ReCS/N band), filled squares: correlated fluxes measured by MIDI. Four possible scenarios are shown: a compact Gaussian distribution with FWHM = 5.8 ± 0.3 pc (grey solid line); an unresolved source plus a partially resolved Gaussian component of ~ 10–80 pc (core-haloconfiguration; light green-shaded area); a power-law distribution with an inner radius of R_in = 0.08 pc, a half-light radius of R_1∕2 = 1.8 pc, an extended dust density distribution (α = 0.5), and a temperature gradient index for ISM grains (β = −0.36; black dotted line); a power-law distribution with an inner radius of R_in = 0.4 pc, R_1∕2 = 7.3 pc, a flat density distribution (α = 0), and a temperature gradient index for ISM grains (β = −0.36; grey dot-dashed line).