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Fig. 8


Diagnostic diagram for the log (Hα/[N ii]) intensity ratio versus log (Hα/[S ii]) ratio showing the locations of SNRs, H ii regions (Riesgo & López 2006), HH objects (Cantó 1981), and the 90% probability ellipse of normal PNs. Also plotted are 551 Galactic PNs (black dots; Acker et al. 1992), HH object sample (brown asterisks; Raga et al. 1996), symbiotic stars (green squares; Luna & Costa 2005), IPHAS young PNs (purple diamonds; Viironen et al. 2009b) and five evolved PNs A35, NGC 650-1, NGC 6583, NGC 7293, and S 176 (red triangles; Sabbadin et al. 1977; Acker et al. 1992) with these new PNs of our sample (blue squares).

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