Predicted dust densities (attenuation per parsec) in the different regions of figure 4 and for two different attenuation errors: 0.1 (left) and 0.01 (right). Red and green crosses show true values for regions 1 and 3 respectively, and blue points show predicted values for different regions (1, 2 and 3 from top to bottom). The error bars on the latter points are also predicted by our model. Although there are no observations in region 2 the model can still predict dust densities there.