Imaging and spectroscopy of compact emission nebulae in NGC 6822

Abstract

We present preliminary results of CTIO 4-m MOSAIC 2 imaging and Magellan and Gemini-South multi-object spectroscopy for NGC 6822. In our on-band off-band ([OIII] 5007, H$\alpha$) MOSAIC 2 data of the whole galaxy, we are searching for Planetary Nebula (PN) candidates and measuring their [OIII] 5007 fluxes. So far we have confirmed 13 of the 17 PN candidates reported previously and some other faint candidates. We obtained Magellan and Gemini-South multi-object spectroscopic data to derive simultaneously, the chemical abundances of some HII regions and PNe. The observed objects are distributed in different zones of the galaxy. Our aim is to obtain the chemical abundances of the present ISM (HII regions) and the corresponding values at the time of formation of the PNe. With these data the chemical homogeneity of NGC 6822 will be tested and 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 NGC 6822.