New eyes on the first stars: the old bulge component and the important role of PNe in this context

5Most of the current observational efforts in finding the chemical imprints left by the first stars have focused on the most metal-poor (and probably oldest) stars found in the MW halo. Very metal-poor stars were also found in ultra-faint dwarf galaxies, which are intriguing dark-matter dominated objects with very low average metallicities. Studies based on the chemical and kinematic properties of stars in the different MW components have shown that not only the halo, but also the bulge is a potential host of some of the oldest stars in our Galaxy. The oldest Globular Cluster of the MW is located in the Bulge (Barbuy et al. 2009), and recently it has been possible to measure ages for microlensed dwarf stars in the Bulge, finding very old objects. These both observational results show that the oldest objects in the Bulge have metallicities around [Fe/H] = -1, hence offering a new window on the First Stars (Chiappini et al. 2011). Indeed, the correspondence between age and metallicity is strongly dependent on the star formation history of the particular studied component, and this suggestion has far reaching implications.What I would like to show in my talk is the importance Planetary Nebulae can play in this hot field. I will show that by studying the PNe metallicity bulge distribution one can highlight the "old Bulge" component. Once this important observational constraint is used to guide chemical evolution models of the oldest bulge population, one can use these models to look for imprints of the first stars in the bulge. A comparison with what we have found so far for the halo, and the new insights we can get by adding the Galactic Bulge in this interesting topic will be shown and discussed.nonenoneChiappini Cristina; Cescutti G; Barbuy Beatriz; Meynet Georges; Hirschi RaphaelChiappini, Cristina; Cescutti, G; Barbuy, Beatriz; Meynet, Georges; Hirschi, Raphae