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

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

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Título Sc and neutron-capture abundances in Galactic low- and high-α field halo stars
Autor Fishlock, Cherie K.
Yong, David
Karakas, Amanda I.
Brito, Alan Alves
Meléndez, Jorge
Nissen, Poul Erik
Kobayashi, Chiaki
Casey, Andrew Raithby
Abstract 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-α halo and thick-disc stars) based on the [α/Fe] abundance ratio and their kinematics as discovered by Nissen & Schuster. We find differences between the low- and high-α 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-α stars have a lower abundance compared to the high-α stars. The low-α 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-α 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-α population. By comparing the low-α population with AGB stellar models, we place constraints on the mass range of the AGB stars.
Contido em Monthly notices of the Royal Astronomical Society. Oxford. Vol. 466, no. 4 (May 2017), p. 4672–4682
Assunto Composicao estelar
Formacao de galaxias
Massa estelar
Metalicidade
[en] Galaxy: halo
[en] Stars: abundances
Origem Estrangeiro
Tipo Artigo de periódico
URI http://hdl.handle.net/10183/168956
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