Posterior probability distribution over the free parameters of the model resulting from the MCMC analysis. See Table 3 for a description of the free parameters. Panels along the diagonal: one-dimensional projections (marginalised over all other parameters) of the probability density function. Off-diagonal panels: two-dimensional projections showing correlations between parameters. The grey-scale colours are proportional to the probability density (normalised per panel). Contours are drawn at 1σ and 2σ levels.