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

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. 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.

Authors:
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Publication Date:
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 Org.:
DES Collaboration; DES
OSTI Identifier:
1419983
Alternate Identifier(s):
OSTI ID: 1422195; OSTI ID: 1422476
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
Resource Type:
Journal Article: 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
Publisher:
Institute of Physics (IOP)
Country of Publication:
United States
Language:
English
Subject:
79 ASTRONOMY AND ASTROPHYSICS; galaxies: abundances; galaxies: dwarf; stars: abundances; stars: chemically peculiar

Citation Formats

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. Chemical Abundance Analysis of Three α-poor, Metal-poor Stars in the Ultrafaint Dwarf Galaxy Horologium I. United States: N. p., 2018. Web. doi:10.3847/1538-4357/aaa01d.
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., & Yanny, B. Chemical Abundance Analysis of Three α-poor, Metal-poor Stars in the Ultrafaint Dwarf Galaxy Horologium I. United States. doi:10.3847/1538-4357/aaa01d.
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. Thu . "Chemical Abundance Analysis of Three α-poor, Metal-poor Stars in the Ultrafaint Dwarf Galaxy Horologium I". United States. doi:10.3847/1538-4357/aaa01d.
@article{osti_1419983,
title = {Chemical Abundance Analysis of Three α-poor, Metal-poor Stars in the Ultrafaint Dwarf Galaxy Horologium I},
author = {Nagasawa, D. Q. and Marshall, J. L. and Li, T. S. and Hansen, T. T. and Simon, J. D. and Bernstein, R. A. and Balbinot, E. and Drlica-Wagner, A. and Pace, A. B. and Strigari, L. E. and Pellegrino, C. M. and DePoy, D. L. and Suntzeff, N. B. and Bechtol, K. and Walker, A. R. and Abbott, T. M. C. and Abdalla, F. B. and Allam, S. and Annis, J. and Benoit-Lévy, A. and Bertin, E. and Brooks, D. and Rosell, A. Carnero and Kind, M. Carrasco and Carretero, J. and Cunha, C. E. and D’Andrea, C. B. and da Costa, L. N. and Davis, C. and Desai, S. and Doel, P. and Eifler, T. F. and Flaugher, B. and Fosalba, P. and Frieman, J. and García-Bellido, J. and Gaztanaga, E. and Gerdes, D. W. and Gruen, D. and Gruendl, R. A. and Gschwend, J. and Gutierrez, G. and Hartley, W. G. and Honscheid, K. and James, D. J. and Jeltema, T. and Krause, E. and Kuehn, K. and Kuhlmann, S. and Kuropatkin, N. and March, M. and Miquel, R. and Nord, B. and Roodman, A. and Sanchez, E. and Santiago, B. and Scarpine, V. and Schindler, R. and Schubnell, M. and Sevilla-Noarbe, I. and Smith, M. and Smith, R. C. and Soares-Santos, M. and Sobreira, F. and Suchyta, E. and Tarle, G. and Thomas, D. and Tucker, D. L. and Wechsler, R. H. and Wolf, R. C. and Yanny, B.},
abstractNote = {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.},
doi = {10.3847/1538-4357/aaa01d},
journal = {The Astrophysical Journal (Online)},
number = 2,
volume = 852,
place = {United States},
year = {Thu Jan 11 00:00:00 EST 2018},
month = {Thu Jan 11 00:00:00 EST 2018}
}

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