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

Research output: Research - peer-reviewJournal article

DOI

  • Cherie K. Fishlock
    Cherie K. FishlockRSPAS, Australian National University
  • D. Yong
    D. YongRSPAS, Australian National University
  • Amanda I. Karakas
    Amanda I. KarakasMonash University
  • Alan Alves Brito
    Alan Alves BritoUniversidade Federal do Rio Grande do Sul
  • J. Meléndez
    J. MeléndezUniversidade de São Paulo
  • P. E. Nissen
  • C. Kobayashi
    C. KobayashiUniversity of Hertfordshire
  • A. R. Casey
    A. R. CaseyCambridge University

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.

Original languageEnglish
JournalRoyal Astronomical Society. Monthly Notices
Volume466
Issue number4
Pages (from-to)4672-4682
Number of pages11
ISSN0035-8711
DOIs
StatePublished - May 2017

    Research areas

  • stars: abundances, Galaxy: halo, ASYMPTOTIC GIANT BRANCH, METAL-POOR STARS, DWARF SPHEROIDAL GALAXIES, CHEMICAL EVOLUTION, R-PROCESS, LOW-METALLICITY, GLOBULAR-CLUSTER, MASSIVE STARS, OLD STARS, MILKY-WAY

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