Chemical abundances of distant extremely metal-poor unevolved stars

Understand

Aims: The purpose of our study is to determine the chemical composition of a sample of 16 candidate Extremely Metal-Poor (EMP) dwarf stars, extracted from the Sloan Digital Sky Survey (SDSS).

• There are two main purposes: in the first place to verify the reliability of the metallicity estimates derived from the SDSS spectra; in the second place to see if the abundance trends found for the brighter nearer stars studied previously also hold for this sample of fainter, more distant stars.
• Methods: We used the UVES at the VLT to obtain high-resolution spectra of the programme stars.
• The abundances were determined by an automatic analysis with the MyGIsFOS code, with the exception of lithium, for which the abundances were determined from the measured equivalent widths of the Li I resonance doublet.