IC10: the history of the nearest starburst galaxy through its Planetary
  Nebula and HII region populations
  We report the results of spectroscopic observations, obtained with the Gemini
North Multi-Object Spectrograph, of 9 planetary nebulae (PNe) and 15 \hii\
regions located in the 5.5\arcmin $\times$5.5\arcmin inner region of the nearby
starburst galaxy IC10. Twelve new candidate PNe have been discovered during our
pre-imaging phase. Nine of them have been spectroscopically confirmed. The
direct availability of the electron temperature diagnostics in several nebulae
allowed an accurate determination of the metallicity map of IC10 at two epochs:
the present-time from \hii regions and the old/intermediate-age from PNe. We
found a non-homogeneous distribution of metals at both epochs, but similar
average abundances were found for the two populations. The derived
age-metallicity relation shows a little global enrichment interpreted as the
loss of metals by SN winds and to differential gas outflows. Finally, we
analyzed the production of oxygen --through the third dredge-up-- in the
chemical abundance patterns of the PN populations belonging to several dwarf
irregular galaxies. We found that the third dredge-up of oxygen is a
metallicity dependent phenomenon occurring mainly for 12+$\log$(O/H)$\leq$7.7
and substantially absent in IC10 PNe.
