Local stars formed at z>10: a sample extracted from the SDSS
  As the Universe emerged from its initial hot and dense phase, its chemical
composition was extremely simple, being limited to stable H and He isotopes,
and traces of Li. The first stars that formed had such initial composition.
However, they quickly began to produce a whole array of heavier nuclei,
polluting the interstellar medium. While none among these first stars has been
detected to date, an increasing sample exists of their direct descendant, stars
with heavy elements content of the order of 1/1000 of the solar value, or less.
In most cases, such stars should have formed at redshift of about 10 or beyond,
and their chemical composition can provide crucial constraints to the nature of
the very first stars. Extremely metal poor (EMP) stars are exceedingly rare. We
used the low resolution spectra obtained by the Sloan Digital Sky Survey (SDSS)
to search for EMP candidates: results of VLT-UVES high resolution follow-up for
16 of them is presented here. A newly developed automatic abundance analysis
and parameter determination code, MyGIsFOS, has been employed to analyze the
detailed chemical abundances of such stars.
