70 μm map of the radiative transfer simulation that produced the brightest nebulosities. These cavities are produced by ‘Model 3’ with a central object luminosity of 4000 L_⊙, a characteristic radius of 10⁴ AU, a characteristic density of 10⁷ cm⁻³ and a cavity density of 10⁴ cm⁻³. This is to be directly compared to Fig. 3 (left). Note the order of magnitude difference in flux density between the two images.