Sc and neutron-capture abundances in Galactic low- and high-alpha field halo stars

Autor(es)

Fishlock, C. K. ; Yong, D. ; Karakas, A. I. ; Alves-Brito, A. ; Melendez, J. ; Nissen, P. E. ; Kobayashi, C. ; Casey, A. R.

• Tipo de documento: Artigo Científico
• Fonte: Monthly Notices of the Royal Astronomical Society; v. 466, n. 4, p. 4672-4682, MAY 2017.
• Citações Web of Science: 8

Resumo

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-a 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. (AU)

• Processo FAPESP: 12/24392-2 - Espectroscopia de alta precisão: impacto no estudo de planetas, estrelas, a galáxia e cosmologia
• Beneficiário: Jorge Luis Melendez Moreno
• Linha de fomento: Auxílio à Pesquisa - Temático
• Processo FAPESP: 14/18100-4 - Populações estelares na Via Láctea: bojo, halo, disco e regiões de formação de estrelas; instrumentação para espectroscopia de alta resolução
• Beneficiário: Beatriz Leonor Silveira Barbuy
• Linha de fomento: Auxílio à Pesquisa - Temático