Chemical abundance analysis of three α-poor, metal-poor stars in the ultrafaint dwarf galaxy Horologium i
Chemical abundance analysis of three α-poor, metal-poor stars in the ultrafaint dwarf galaxy Horologium i
We present chemical abundance measurements of three stars in the ultrafaint dwarf galaxy Horologium I, a Milky Way satellite discovered by the Dark Energy Survey. Using high-resolution spectroscopic observations, we measure the metallicity of the three stars, as well as abundance ratios of several α-elements, iron-peak elements, and neutron-capture elements. The abundance pattern is relatively consistent among all three stars, which have a low average metallicity of [Fe/H] ∼ -2.6 and are not α-enhanced ([α/Fe] ∼ 0.0). This result is unexpected when compared to other low-metallicity stars in the Galactic halo and other ultrafaint dwarfs and suggests the possibility of a different mechanism for the enrichment of Hor I compared to other satellites. We discuss possible scenarios that could lead to this observed nucleosynthetic signature, including extended star formation, enrichment by a Population III supernova, and or an association with the Large Magellanic Cloud.
galaxies: abundances, galaxies: dwarf, stars: abundances, stars: chemically peculiar
Nagasawa, D.Q.
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Marshall, J.L.
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Li, T.S.
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Hansen, T.T.
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Simon, J.D.
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Bernstein, R.A.
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Balbinot, E.
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Drlica-Wagner, A.
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Depoy, D.L.
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Bechtol, K.
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Annis, J.
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Wechsler, R.H.
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January 2018
Nagasawa, D.Q.
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Marshall, J.L.
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Li, T.S.
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Hansen, T.T.
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Simon, J.D.
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Bernstein, R.A.
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Balbinot, E.
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Drlica-Wagner, A.
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Pace, A.B.
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Strigari, L.E.
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Pellegrino, C.M.
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Depoy, D.L.
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Suntzeff, N.B.
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Bechtol, K.
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Walker, A.R.
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Abdalla, F.B.
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Allam, S.
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Annis, J.
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Benoit-Lévy, A.
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Rosell, A. Carnero
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Kind, M. Carrasco
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Cunha, C. E.
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