Marginalized 2D and 1D posterior PDFs of the scaling relation parameters (slope α, normalization , and intrinsic scatter Δσ_ap around the Faber-Jackson relation) obtained from fitting the measured velocity dispersions of 15 cluster galaxies. The dashed vertical lines in the histograms show the median and the 16th and 84th percentiles of the marginalized 1D distributions of each parameter. The parameter values are reported on the top of each figure.