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Title: 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. Here, 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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Publication Date:
Report Number(s):
arXiv:1708.02290; FERMILAB-PUB-17-300-AE
Journal ID: ISSN 1538-4357; TRN: US1801431
Grant/Contract Number:
AC02-76SF00515; AC05-00OR22725; AC02-07CH11359; 240672; 291329; 306478; AYA2015-71825; ESP2015-88861; FPA2015-68048; SEV-2012-0234; SEV-2016-0597; MDM-2015-0509; AST-1138766; AST-1536171
Accepted Manuscript
Journal Name:
The Astrophysical Journal (Online)
Additional Journal Information:
Journal Name: The Astrophysical Journal (Online); Journal Volume: 852; Journal Issue: 2; Journal ID: ISSN 1538-4357
Institute of Physics (IOP)
Research Org:
SLAC National Accelerator Lab., Menlo Park, CA (United States); Argonne National Lab. (ANL), Argonne, IL (United States); Fermi National Accelerator Lab. (FNAL), Batavia, IL (United States); Oak Ridge National Lab. (ORNL), Oak Ridge, TN (United States)
Sponsoring Org:
USDOE Office of Science (SC), Advanced Scientific Computing Research (ASCR) (SC-21); European Union (EU); National Science Foundation (NSF); Ministry of Economy and Competitiveness (MINECO); USDOE Office of Science (SC), High Energy Physics (HEP) (SC-25)
Contributing Orgs:
DES Collaboration; DES
Country of Publication:
United States
79 ASTRONOMY AND ASTROPHYSICS; galaxies: abundances; galaxies: dwarf; stars: abundances; stars: chemically peculiar
OSTI Identifier:
Alternate Identifier(s):
OSTI ID: 1422195; OSTI ID: 1422476