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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
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
0004-637X
Nagasawa, D.Q.
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Marshall, J.L.
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Li, T.S.
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Nagasawa, D.Q., Marshall, J.L., Li, T.S., Hansen, T.T., Simon, J.D., Bernstein, R.A., Balbinot, E., Drlica-Wagner, A., Pace, A.B., Strigari, L.E., Pellegrino, C.M., Depoy, D.L., Suntzeff, N.B., Bechtol, K., Walker, A.R., Abbott, T.M.C., Abdalla, F.B., Allam, S., Annis, J., Benoit-Lévy, A., Bertin, E., Brooks, D., Rosell, A. Carnero, Kind, M. Carrasco, Carretero, J., Cunha, C. E., D'Andrea, C.B., Da Costa, L.N., Davis, C., Desai, S., Doel, P., Eifler, T.F., Flaugher, B., Fosalba, P., Frieman, J., García-Bellido, J., Gaztanaga, E., Gerdes, D.W., Gruen, D., Gruendl, R.A., Gschwend, J., Gutierrez, G., Hartley, W.G., Honscheid, K., James, D.J., Jeltema, T., Krause, E., Kuehn, K., Kuhlmann, S., Kuropatkin, N., March, M., Miquel, R., Nord, B., Roodman, A., Sanchez, E., Santiago, B., Scarpine, V., Schindler, R., Schubnell, M., Sevilla-Noarbe, I., Smith, M., Smith, R.C., Soares-Santos, M., Sobreira, F., Suchyta, E., Tarle, G., Thomas, D., Tucker, D.L., Wechsler, R.H., Wolf, R.C. and Yanny, B. (2018) Chemical abundance analysis of three α-poor, metal-poor stars in the ultrafaint dwarf galaxy Horologium i. The Astrophysical Journal, 852 (2). (doi:10.3847/1538-4357/aaa01d).

Record type: Article

Abstract

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.

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More information

Accepted/In Press date: 5 December 2017
e-pub ahead of print date: 11 January 2018
Published date: January 2018
Keywords: galaxies: abundances, galaxies: dwarf, stars: abundances, stars: chemically peculiar

Identifiers

Local EPrints ID: 419819
URI: https://eprints.soton.ac.uk/id/eprint/419819
ISSN: 0004-637X
PURE UUID: 90786e90-08ab-4042-88bd-c6ca32b7dff2
ORCID for M. Smith: ORCID iD orcid.org/0000-0002-3321-1432

Catalogue record

Date deposited: 20 Apr 2018 16:31
Last modified: 15 Aug 2019 00:33

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Contributors

Author: D.Q. Nagasawa
Author: J.L. Marshall
Author: T.S. Li
Author: T.T. Hansen
Author: J.D. Simon
Author: R.A. Bernstein
Author: E. Balbinot
Author: A. Drlica-Wagner
Author: A.B. Pace
Author: L.E. Strigari
Author: C.M. Pellegrino
Author: D.L. Depoy
Author: N.B. Suntzeff
Author: K. Bechtol
Author: A.R. Walker
Author: T.M.C. Abbott
Author: F.B. Abdalla
Author: S. Allam
Author: J. Annis
Author: A. Benoit-Lévy
Author: E. Bertin
Author: D. Brooks
Author: A. Carnero Rosell
Author: M. Carrasco Kind
Author: J. Carretero
Author: C. E. Cunha
Author: C.B. D'Andrea
Author: L.N. Da Costa
Author: C. Davis
Author: S. Desai
Author: P. Doel
Author: T.F. Eifler
Author: B. Flaugher
Author: P. Fosalba
Author: J. Frieman
Author: J. García-Bellido
Author: E. Gaztanaga
Author: D.W. Gerdes
Author: D. Gruen
Author: R.A. Gruendl
Author: J. Gschwend
Author: G. Gutierrez
Author: W.G. Hartley
Author: K. Honscheid
Author: D.J. James
Author: T. Jeltema
Author: E. Krause
Author: K. Kuehn
Author: S. Kuhlmann
Author: N. Kuropatkin
Author: M. March
Author: R. Miquel
Author: B. Nord
Author: A. Roodman
Author: E. Sanchez
Author: B. Santiago
Author: V. Scarpine
Author: R. Schindler
Author: M. Schubnell
Author: I. Sevilla-Noarbe
Author: M. Smith ORCID iD
Author: R.C. Smith
Author: M. Soares-Santos
Author: F. Sobreira
Author: E. Suchyta
Author: G. Tarle
Author: D. Thomas
Author: D.L. Tucker
Author: R.H. Wechsler
Author: R.C. Wolf
Author: B. Yanny

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