Abstract
| Lucchesi |
|---|
| Chemical evolution of dwarf galaxies |
| I will present my results on the chemical analysis of (Extremely) Metal-Poor (EMP, [Fe/H]<-3) stars in different environments. EMP stars are very old and very rare objects. They carry the imprint of the chemical composition of the early Universe. Dwarf galaxies are the building blocs of bigger galaxies, and because of their extra-galactic nature, it is very challenging to find and analyze their EMP stellar population. With 12 EMP stars, Sculptor is the most studied dwarf galaxy to date. I will present my analysis of some EMP stars in the Sextans, Fornax and Carina dwarf spheroidal galaxies (dSph). First, their similarities in the alpha-elements group compared to the Milky Way halo and the Ultra Faint Dwarf galaxies (UFDs). Then, the apparent divergence when the fraction of Carbon-Enhanced Metal-Poor (CEMP) stars are compared in these systems. The formation sites of neutron-capture elements are also not perfectly identified: - the light neutron-capture strontium appears to be produced earlier than the heavier barium element in dSphs, but not in UFDs. - the first discovery of an EMP r-process rich star in a dSph suggest violent events such as neutron-star mergers in the early history of Fornax. In a second part I will present the results from multi-fiber spectrograph observations of 60 stars in one outskirt region of Sculptor. Thanks to previous observations in the center of this dwarf, we will be able to draw a first spatially characterized chemical overview of Sculptor. |