Using neutron-capture abundances as a tracer of Galactic halo formation

Chemical differences in stellar populations are one method to study the formation and evolution of the Galactic halo of the Milky Way. In particular, there are low α-element stars and high α-element stars in the Galactic halo that also show differences in their neutron-capture elemental abundances. Asymptotic giant branch (AGB) stars are an important source of neutron-capture elements that are produced via the slow (s-) neutron-capture process. To better understand these abundance differences, models of AGB stars have been calculated at a metallicity of Z = 0.001 ([Fe/H] ≈ -1.2). We present theoretical abundance predictions of H through to Pb from low-mass AGB stars spanning amass range of 1M_ȯ to 3M_ȯ. We compare the abundance distribution of the 1.5M_ȯ stellar model to that of Cristallo et al. (2011) and find that they are in good agreement. Finally, we compare final surface abundances from stellar models of 1M _ȯ and 3M_ȯ, Z = 0.001 that have been computed using two different nuclear networks. We find small abundance differences in the s-process peaks for the 1M_ȯ but no differences in the neutron-capture elements for the 3M₀ model.