Program: GS-2005B-Q-56

We propose to use GMOS (multi-object) to derive simultaneoulsy, the chemical abundances of some HII regions and PNe of the dIrr NGC 6822. The objects are distributed in different zones of the galaxy. Thus, we will obtain the abundances of the present ISM (HII regions) and the corresponding values at the time of formation of the PNe. The chemical homogeneity of NGC6822 will be tested. The abundance pattern given by HII regions and PNe will be used as an observational constrain for computing chemical evolution models to infer the chemical history of NGC6822. This galaxy is well suited for this study because, due to its position in the Local Group, apparently it has not lost significant amount of gas by tidal effects, and its star formartion history is known. A well constrained chemical evolution model would help to decide on the controversy if O-rich galactic outflows have occurred in irregulars.