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Chemical Abundance Analysis of Three α-poor, Metal-poor Stars in the Ultrafaint Dwarf Galaxy Horologium I

Nagasawa, D. Q. and Eifler, T. F. (2018) Chemical Abundance Analysis of Three α-poor, Metal-poor Stars in the Ultrafaint Dwarf Galaxy Horologium I. Astrophysical Journal, 852 (2). Art. No. 99. ISSN 0004-637X. https://resolver.caltech.edu/CaltechAUTHORS:20180116-142141787

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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.


Item Type:Article
Related URLs:
URLURL TypeDescription
https://doi.org/10.3847/1538-4357/aaa01dDOIArticle
http://iopscience.iop.org/article/10.3847/1538-4357/aaa01d/metaPublisherArticle
https://arxiv.org/abs/1708.02290arXivDiscussion Paper
ORCID:
AuthorORCID
Eifler, T. F.0000-0002-1894-3301
Additional Information:© 2018 The American Astronomical Society. Received 2017 August 7. Accepted 2017 December 5. Published 2018 January 11. D.Q.N. wishes to thank the referee, Chris Sneden, for his insightful comments. He also thanks Katelyn Stringer for editorial comments. E.B. acknowledges financial support from the European Research Council (ERC-StG-335936). C.M.P. was supported by NSF grant AST-1560223, "REU Site: Astronomical Research and Instrumentation at Texas A&M University." Funding for the DES Projects has been provided by the U.S. Department of Energy, the U.S. National Science Foundation, the Ministry of Science and Education of Spain, the Science and Technology Facilities Council of the United Kingdom, the Higher Education Funding Council for England, the National Center for Supercomputing Applications at the University of Illinois at Urbana-Champaign, the Kavli Institute of Cosmological Physics at the University of Chicago, the Center for Cosmology and Astro-Particle Physics at the Ohio State University, the Mitchell Institute for Fundamental Physics and Astronomy at Texas A&M University, Financiadora de Estudos e Projetos, Fundação Carlos Chagas Filho de Amparo à Pesquisa do Estado do Rio de Janeiro, Conselho Nacional de Desenvolvimento Científico e Tecnológico and the Ministério da Ciência, Tecnologia e Inovação, the Deutsche Forschungsgemeinschaft, and the Collaborating Institutions in the Dark Energy Survey. The Collaborating Institutions are Argonne National Laboratory, the University of California at Santa Cruz, the University of Cambridge, Centro de Investigaciones Energéticas, Medioambientales y Tecnológicas-Madrid, the University of Chicago, University College London, the DES-Brazil Consortium, the University of Edinburgh, the Eidgenössische Technische Hochschule (ETH) Zürich, Fermi National Accelerator Laboratory, the University of Illinois at Urbana-Champaign, the Institut de Ciències de l'Espai (IEEC/CSIC), the Institut de Física d'Altes Energies, Lawrence Berkeley National Laboratory, the Ludwig-Maximilians Universität München and the associated Excellence Cluster Universe, the University of Michigan, the National Optical Astronomy Observatory, the University of Nottingham, The Ohio State University, the University of Pennsylvania, the University of Portsmouth, SLAC National Accelerator Laboratory, Stanford University, the University of Sussex, Texas A&M University, and the OzDES Membership Consortium. Based in part on observations at Cerro Tololo Inter-American Observatory, National Optical Astronomy Observatory, which is operated by the Association of Universities for Research in Astronomy (AURA) under a cooperative agreement with the National Science Foundation. The DES data management system is supported by the National Science Foundation under grant nos. AST-1138766 and AST-1536171. The DES participants from Spanish institutions are partially supported by MINECO under grants AYA2015-71825, ESP2015-88861, FPA2015-68048, SEV-2012-0234, SEV-2016-0597, and MDM-2015-0509, some of which include ERDF funds from the European Union. IFAE is partially funded by the CERCA program of the Generalitat de Catalunya. Research leading to these results has received funding from the European Research Council under the European Union's Seventh Framework Program (FP7/2007-2013), including ERC grant agreements 240672, 291329, and 306478. We acknowledge support from the Australian Research Council Centre of Excellence for All-sky Astrophysics (CAASTRO), through project no. CE110001020. This manuscript has been authored by Fermi Research Alliance LLC under contract no. DE-AC02-07CH11359 with the U.S. Department of Energy, Office of Science, Office of High Energy Physics. The U.S. Government retains and the publisher, by accepting the article for publication, acknowledges that the U.S. Government retains a nonexclusive, paid-up, irrevocable, worldwide license to publish or reproduce the published form of this manuscript, or allow others to do so, for U.S. Government purposes. IRAF is distributed by the National Optical Astronomy Observatory, which is operated by the Association of Universities for Research in Astronomy (AURA) under a cooperative agreement with the National Science Foundation. This paper has gone through internal review by the DES Collaboration.
Funders:
Funding AgencyGrant Number
European Research Council (ERC)335936
NSFAST-1560223
Department of Energy (DOE)UNSPECIFIED
Ministerio de Educación y Ciencia (MEC)UNSPECIFIED
Science and Technology Facilities Council (STFC)UNSPECIFIED
Higher Education Funding Council for EnglandUNSPECIFIED
National Center for Supercomputing Applications (NCSA)UNSPECIFIED
Kavli Institute for Cosmological PhysicsUNSPECIFIED
Ohio State University Center for Cosmology and Astro-Particle PhysicsUNSPECIFIED
Texas A&M UniversityUNSPECIFIED
Financiadora de Estudos e ProjetosUNSPECIFIED
Fundação Carlos Chagas Filho de Amparo à Pesquisa do Estado do Rio de Janeiro (FAPERJ)UNSPECIFIED
Conselho Nacional de Desenvolvimento Científico e Tecnológico (CNPq)UNSPECIFIED
Ministério da Ciência Tecnologia e InovaçãoUNSPECIFIED
Deutsche Forschungsgemeinschaft (DFG)UNSPECIFIED
NSFAST-1138766
NSFAST-1536171
Ministerio de Economía, Industria y Competitividad (MINECO)AYA2015-71825
Ministerio de Economía, Industria y Competitividad (MINECO)ESP2015-88861
Ministerio de Economía, Industria y Competitividad (MINECO)FPA2015-68048
Centro de Excelencia Severo OchoaSEV-2012-0234
Centro de Excelencia Severo OchoaSEV-2016-0597
Ministerio de Economía, Industria y Competitividad (MINECO)MDM-2015-0509
CERCAUNSPECIFIED
European Community's Seventh Framework ProgramFP7/2007-2013
European Research Council (ERC)240672
European Research Council (ERC)291329
European Research Council (ERC)306478
Australian Research CouncilCE110001020
Department of Energy (DOE)DE-AC02-07CH11359
Subject Keywords:galaxies: abundances; galaxies: dwarf; stars: abundances; stars: chemically peculiar
Issue or Number:2
Record Number:CaltechAUTHORS:20180116-142141787
Persistent URL:https://resolver.caltech.edu/CaltechAUTHORS:20180116-142141787
Official Citation:D. Q. Nagasawa et al 2018 ApJ 852 99
Usage Policy:No commercial reproduction, distribution, display or performance rights in this work are provided.
ID Code:84344
Collection:CaltechAUTHORS
Deposited By: Ruth Sustaita
Deposited On:17 Jan 2018 18:57
Last Modified:09 Mar 2020 13:18

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