Program: GN-2005B-C-9

We propose to map the physical conditions of the interstellar medium (ISM) and to characterise the stellar population in 5 extremely metal-poor ($<0.05$ solar metallicity) emission-line galaxies recently discovered (Koo et al 2005, Kniazev et al 2003). We define very metal-poor galaxies as those having $12+log(O/H)<7.65$. (IZw18 has $12+log(O/H)\sim7.2$). Our targets have redshifts between 0.003 and 0.04. These very rare galaxies (0.005\% of the galaxy population out to $r'=19.5$) are unique laboratories that provide us with the opportunity to study extreme conditions of the ISM and the stellar populations in order to better understand the chemical enrichment of galaxies. Here, we want to learn where the star formation occurs within these galaxies by measuring the two-dimensional distribution of hydrogen emission. We would like to know if the emission is in a particular component (nucleus/disk) or scattered in regions across the galaxies. We aim to map the metallicity by targeting [OII] 3727 and [OIII]4959/5007 and answer the question of whether the pollution is located in the same places where the star formation occurs or whether they are offset, or not linked in any way. Ultimately, measuring the physical properties of galaxies in situ will provide us with a quantitative way of studying galaxy morphology. By characterizing the physical properties of the ISM of a sample of galaxies spanning a range in morphological types, and then associating this characterization with the apparent galaxy morphology, we hope to tie the latter into a quantitative, and physically-based framework (Takamiya 1999).