New information on the relations between the Galactic disks , the halo , and satellite galaxies is being obtained from elemental abundances of stars having metallicities in the range -1.5 < [ Fe/H ] < -0.5 .
The first results for a sample of 26 halo stars and 13 thick-disk stars observed with the ESO VLT/UVES spectrograph are presented .
The halo stars fall in two distinct groups : one group ( 9 stars ) has [ \alpha /Fe ] = 0.30 \pm 0.03 like the thick-disk stars .
The other group ( 17 stars ) shows a clearly deviating trend ranging from [ \alpha /Fe ] = 0.20 at [ Fe/H ] = -1.3 to [ \alpha /Fe ] = 0.08 at [ Fe/H ] = -0.8 .
The kinematics of the stars are discussed and the abundance ratios Na/Fe , Ni/Fe , Cu/Fe and Ba/Y are applied to see if the “ low-alpha ” stars are connected to the thin disk or to Milky Way satellite galaxies .
Furthermore , we compare our data with simulations of chemical abundance distributions in hierarchically formed stellar halos in a \Lambda CDM Universe .