Distance from cluster centre (pc) versus v_out (kms⁻¹). The uncertainties for members of λ Ori are in red. The best-fitting gradients and the 16 and 84th percentiles values of the fit are shown as solid and dashed lines respectively in each panel. The best-fit gradient (rate of expansion) and uncertainties are given in kms⁻¹ pc⁻¹ as well as the corresponding timescale of expansion and uncertainties in Myrs.