The best-fit plots for each sample investigated. Top panels: the χ² contour plot for δ = 0, white areas denote χ² values much larger than the colour scale shown. Only the contour of δ = 0 is displayed as the fits begin to get worse when δ starts to increase. The black lines denote the maximum χ² to be an acceptable fit to the 1% level. Bottom panels: the χ² values for all of the best-fits in δ space, depicting the worst fits for progressively increasing δ.