Distribution of the parameter values for the fit with two VNEI components. The labels of the data points are region numbers. The lines in the diagrams for surface brightness norm_1,2/A against temperature kT_1,2 (upper and middle panels) show the isobars for p/k = 10⁶ cm^-3 K (blue) and 10⁷ cm^-3 K (green) for different values of the filling factors in the remnant and the size of the emitting volume along the line of sight. The line for each filling factor with the lowest norm_1,2/A are marked with a thicker line and labelled with the f_1,2 value. The lines in the diagram showing the surface brightness as norm₂/A against the ionisation timescale τ₂ (bottom panel) are isochrones for t = 10   000, 20 000, 50 000, and 100 000 yr. A range for all isochrones is shown for each t covering the range of variation in the depth of the emitting volume.