A high resolution VLT/FLAMES study of individual stars in the centre of the Fornax dwarf spheroidal galaxy
ASTRONOMY & ASTROPHYSICS(2018)
摘要
For the first time we show the detailed late-stage chemical evolution history
of small nearby dwarf spheroidal galaxy in the Local Group. We present the
results of a high resolution (R$\sim$20000) FLAMES/GIRAFFE abundance study at
ESO/VLT of 81 photometrically selected red giant branch stars in the central
25$'$ of the Fornax dwarf spheroidal galaxy. We present abundances of \alfe\
(Mg, Si, Ca and Ti), iron-peak elements (Fe, Ni and Cr) and heavy elements (Y,
Ba, La, Nd and Eu). Our sample was randomly selected, and is clearly dominated
by the younger and more metal rich component of Fornax which represents the
major fraction of stars in the central region. This means that the majority of
our stars are 1$-$4~Gyr old, and thus represent the end phase of chemical
evolution in this system. Our sample of stars has unusually low [$\alpha$/Fe],
[Ni/Fe] and [Na/Fe] compared to the Milky Way stellar populations at the same
[Fe/H]. The particularly important role of stellar winds from low metallicity
AGB stars in the creation of s-process elements is clearly seen from the high
[Ba/Y]. Furthermore, we present evidence for an s-process contribution to Eu.
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关键词
galaxies: formation,galaxies: individual: fornax dwarf galaxy,stars: abundances,galaxies: evolution,galaxies: dwarf,galaxies: stellar content,milky way,dwarf galaxies,iron,high resolution
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