We determine relative abundance ratios for the neutron-capture elements Zr , La , Ce , Nd , and Eu for a sample of 27 Galactic dwarf stars with -1.5 < [ Fe/H ] < -0.8 .
We also measure the iron-peak element Sc .
These stars separate into three populations ( low- and high- \alpha halo and thick-disc stars ) based on the [ \alpha /Fe ] abundance ratio and their kinematics as discovered by Nissen & Schuster .
We find differences between the low- and high- \alpha groups in the abundance ratios of [ Sc/Fe ] , [ Zr/Fe ] , [ La/Zr ] , [ Y/Eu ] , and [ Ba/Eu ] when including Y and Ba from Nissen & Schuster .
For all ratios except [ La/Zr ] , the low- \alpha stars have a lower abundance compared to the high- \alpha stars .
The low- \alpha stars display the same abundance patterns of high [ Ba/Y ] and low [ Y/Eu ] as observed in present-day dwarf spheroidal galaxies , although with smaller abundance differences , when compared to the high- \alpha stars .
These distinct chemical patterns have been attributed to differences in the star formation rate between the two populations and the contribution of low-metallicity , low-mass asymptotic giant branch ( AGB ) stars to the low- \alpha population .
By comparing the low- \alpha population with AGB stellar models , we place constraints on the mass range of the AGB stars .