Program: GS-2008B-Q-76

In the framework of the Local Group Census (LGC), a narrow- and broad-band imaging survey of the Local Group galaxies, which was aimed at surveying their populations with strong emission lines, we have searched for planetary nebulae (PNe) in many LG galaxies, including the low-metallicity dwarf irregular galaxy IC 1613 (Magrini et al. 2005). Two new candidate PNe have been found in IC 1613. The aim of this proposal is to obtain deep spectroscopy in order to confirm their nature as PNe and to study their physicochemical properties. These PNe are expected to have very low metallicities (Z). Their study will be CRUCIAL as, together with the single PN of WLM, they are the ONLY extragalactic PNe for which we could accurately derive chemical abundances and understand the nucleosynthetic processes and surface chemical enrichment in low and intermediate-mass stars of a very low Z environment. In particular, we would check if oxygen abundances are left unmodified in the low Z regime during the lifetime of the progenitor as predicted by recent theories (e.g. Marigo et al. 2003, Herwig 2001), or not. The expected results will rigorously test the FUNDAMENTAL assumption made by many authors, who use the oxygen abundance in PNe to probe the metallicity of the ISM at the time that their progenitor stars were formed, and then use it to constrain chemical evolution models (e.g. Maciel et al. 2006). In addition, the comparison of chemical abundances in PNe and HII regions will allow us to constrain the chemical evolution history of this galaxy via means of chemical evolution models (i.e. homogeneity of chemical abundance of HII regions, presence of the ``abundance gap'', etc.), as we have already done for M33 (Magrini et al. 2007).