Left: parameter space n_H, U, Z, as in Fig. 12, but for component BLUE. As in that case, data points were computed from the emission line ratios referring to the median values in Table 6. The individual contour line was smoothed with a Gaussian kernel. Right: the plane log U vs. log Z. The outer isophotal contours delimit the region χ_min + 1, where the χ_min is the value after smoothing with a Gaussian filter. The low- and high-ionization solutions are marked.