García-Hernández, D. A.D. A.García-HernándezVENTURA, PaoloPaoloVENTURADelgado-Inglada, G.G.Delgado-IngladaDell'Agli, FlaviaFlaviaDell'AgliDI CRISCIENZO, MarcellaMarcellaDI CRISCIENZOYagüe, A.A.Yagüe2020-06-292020-06-2920160035-8711http://hdl.handle.net/20.500.12386/26254The abundance of O in planetary nebulae (PNe) has been historically used as a metallicity indicator of the interstellar medium (ISM), where they originated; e.g. it has been widely used to study metallicity gradients in our Galaxy and beyond. However, clear observational evidence for O self-enrichment in low-metallicity Galactic PNe with C-rich dust has been recently reported. Here, we report asymptotic giant branch (AGB) nucleosynthesis predictions for the abundances of the CNO elements and helium in the metallicity range Z<SUB>☉</SUB>/4 < Z < 2 Z<SUB>☉</SUB>. Our AGB models, with diffusive overshooting from all the convective borders, predict that O is overproduced in low-Z low-mass (∼1-3 M<SUB>☉</SUB>) AGB stars and nicely reproduce the recent O overabundances observed in C-rich dust PNe. This confirms that O is not always a good proxy of the original ISM metallicity and other chemical elements such as Cl or Ar should be used instead. The production of oxygen by low-mass stars should be thus considered in galactic-evolution models.STAMPAenArticle10.1093/mnrasl/slw0292-s2.0-84963568324000374226300025https://academic.oup.com/mnrasl/article/458/1/118/25897472016MNRAS.458L.118GFIS/05 - ASTRONOMIA E ASTROFISICAERC sectors::Physical Sciences and Engineering::PE9 Universe sciences: astro-physics/chemistry/biology; solar systems; stellar, galactic and extragalactic astronomy, planetary systems, cosmology, space science, instrumentation