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Fig. 6


Behaviour of 12 + log (Ar/H) vs. 12 + log (O/H). In red the H ii regions. The linear fits, including only PNe, corresponds to 12 + log (Ar/H) = (0.494 ± 0.512) + (0.768 ± 0.064) × (12 + log (O/H)), with r = 0.79. The stellar evolution models for Z = 0.001 by Fishlock et al. (2014, F14) are included.

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