Posterior probability distributions for the colours excess ratio β_H and the intercept of the linear fit in the L1641/L1647 region (l > 210°) when restricting the sample to various J − K_S colour thresholds. For example, for the J − K_S = 1 mag threshold only source above this limit are fitted. The different thresholds are shown in increasingly dark blue colours and, similar to Fig. 6, the ellipses represent 3-sigma covariances of the parameter distribution. The histograms represent kernel densities for each parameter of the fit.