The chemical history of the nearest starburst galaxy – IC10

The irregular dwarf galaxy IC10 is located within the Local Group (LG) at a distance of 750 kpc. Although several studies have revealed the existence of stellar populations with a broad range of ages, its star formation history (SFH) and age-metallicity (AM) relationship remain quite unknown. In this contribution we present our spectroscopic investigation of 15 H ii regions, 9 planetary nebulae (PNe) and 1 symbiotic star –so far the farthest known symbiotic binary. Our main goal is to reconstruct the SFH of IC10 and to constrain its AM relationship using young and intermediate-age stars. The direct availability of the electron temperature in our emission-line spectra allows an accurate determination of the IC10 metallicity map at two different epochs. We find a non-homogeneous distribution of metals at both epochs, but similar average abundances for the two analyzed populations. The derived AM relationship shows a little global enrichment, which is interpreted as due to the loss of metals by supernovae winds and to differential gas outflows. Our results bring strong observational constraints to the chemical enrichment history of IC10, the formation of dwarf irregular galaxies and the evolution of the LG as well.