COMPLETE ELEMENT ABUNDANCES OF NINE STARS IN THE r-PROCESS GALAXY RETICULUM II
We present chemical abundances derived from high-resolution Magellan/Magellan Inamori Kyocera Echelle spectra of the nine brightest known red giant members of the ultra-faint dwarf galaxy Reticulum II (Ret II). These stars span the full metallicity range of Ret II (−3.5 < [Fe/H] < −2). Seven o...
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| Format: | Article |
| Language: | en_US |
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IOP Publishing
2017
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| Online Access: | http://hdl.handle.net/1721.1/108380 https://orcid.org/0000-0002-4863-8842 https://orcid.org/0000-0002-2139-7145 https://orcid.org/0000-0002-7155-679X |
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| author | Simon, Joshua D. Ji, Alexander Pung Frebel, Anna L. Chiti, Anirudh |
| author2 | Massachusetts Institute of Technology. Department of Physics |
| author_facet | Massachusetts Institute of Technology. Department of Physics Simon, Joshua D. Ji, Alexander Pung Frebel, Anna L. Chiti, Anirudh |
| author_sort | Simon, Joshua D. |
| collection | MIT |
| description | We present chemical abundances derived from high-resolution Magellan/Magellan Inamori Kyocera Echelle spectra of the nine brightest known red giant members of the ultra-faint dwarf galaxy Reticulum II (Ret II). These stars span the full metallicity range of Ret II (−3.5 < [Fe/H] < −2). Seven of the nine stars have extremely high levels of r-process material ([Eu/Fe] ~ 1.7), in contrast to the extremely low neutron-capture element abundances found in every other ultra-faint dwarf galaxy studied to date. The other two stars are the most metal-poor stars in the system ([Fe/H] < −3), and they have neutron-capture element abundance limits similar to those in other ultra-faint dwarf galaxies. We confirm that the relative abundances of Sr, Y, and Zr in these stars are similar to those found in r-process halo stars, but they are ~0.5 dex lower than the solar r-process pattern. If the universal r-process pattern extends to those elements, the stars in Ret II display the least contaminated known r-process pattern. The abundances of lighter elements up to the iron peak are otherwise similar to abundances of stars in the halo and in other ultra-faint dwarf galaxies. However, the scatter in abundance ratios is large enough to suggest that inhomogeneous metal mixing is required to explain the chemical evolution of this galaxy. The presence of low amounts of neutron-capture elements in other ultra-faint dwarf galaxies may imply the existence of additional r-process sites besides the source of r-process elements in Ret II. Galaxies like Ret II may be the original birth sites of r-process enhanced stars now found in the halo. |
| first_indexed | 2024-09-23T16:09:04Z |
| format | Article |
| id | mit-1721.1/108380 |
| institution | Massachusetts Institute of Technology |
| language | en_US |
| last_indexed | 2024-09-23T16:09:04Z |
| publishDate | 2017 |
| publisher | IOP Publishing |
| record_format | dspace |
| spelling | mit-1721.1/1083802022-09-29T18:35:22Z COMPLETE ELEMENT ABUNDANCES OF NINE STARS IN THE r-PROCESS GALAXY RETICULUM II Simon, Joshua D. Ji, Alexander Pung Frebel, Anna L. Chiti, Anirudh Massachusetts Institute of Technology. Department of Physics MIT Kavli Institute for Astrophysics and Space Research Ji, Alexander Pung Frebel, Anna L. Chiti, Anirudh We present chemical abundances derived from high-resolution Magellan/Magellan Inamori Kyocera Echelle spectra of the nine brightest known red giant members of the ultra-faint dwarf galaxy Reticulum II (Ret II). These stars span the full metallicity range of Ret II (−3.5 < [Fe/H] < −2). Seven of the nine stars have extremely high levels of r-process material ([Eu/Fe] ~ 1.7), in contrast to the extremely low neutron-capture element abundances found in every other ultra-faint dwarf galaxy studied to date. The other two stars are the most metal-poor stars in the system ([Fe/H] < −3), and they have neutron-capture element abundance limits similar to those in other ultra-faint dwarf galaxies. We confirm that the relative abundances of Sr, Y, and Zr in these stars are similar to those found in r-process halo stars, but they are ~0.5 dex lower than the solar r-process pattern. If the universal r-process pattern extends to those elements, the stars in Ret II display the least contaminated known r-process pattern. The abundances of lighter elements up to the iron peak are otherwise similar to abundances of stars in the halo and in other ultra-faint dwarf galaxies. However, the scatter in abundance ratios is large enough to suggest that inhomogeneous metal mixing is required to explain the chemical evolution of this galaxy. The presence of low amounts of neutron-capture elements in other ultra-faint dwarf galaxies may imply the existence of additional r-process sites besides the source of r-process elements in Ret II. Galaxies like Ret II may be the original birth sites of r-process enhanced stars now found in the halo. National Science Foundation (U.S.) (Grant PHY-1430152) National Science Foundation (U.S.) (CAREER Grant AST-1255160) 2017-04-24T18:50:17Z 2017-04-24T18:50:17Z 2016-10 Article http://purl.org/eprint/type/JournalArticle 1538-4357 http://hdl.handle.net/1721.1/108380 Ji, Alexander P. et al. “COMPLETE ELEMENT ABUNDANCES OF NINE STARS IN THE R -PROCESS GALAXY RETICULUM II.” The Astrophysical Journal 830.2 (2016): 93. © 2016 The American Astronomical Society https://orcid.org/0000-0002-4863-8842 https://orcid.org/0000-0002-2139-7145 https://orcid.org/0000-0002-7155-679X en_US http://dx.doi.org/10.3847/0004-637x/830/2/93 Astrophysical Journal Article is made available in accordance with the publisher's policy and may be subject to US copyright law. Please refer to the publisher's site for terms of use. application/pdf IOP Publishing American Astronomical Society |
| spellingShingle | Simon, Joshua D. Ji, Alexander Pung Frebel, Anna L. Chiti, Anirudh COMPLETE ELEMENT ABUNDANCES OF NINE STARS IN THE r-PROCESS GALAXY RETICULUM II |
| title | COMPLETE ELEMENT ABUNDANCES OF NINE STARS IN THE r-PROCESS GALAXY RETICULUM II |
| title_full | COMPLETE ELEMENT ABUNDANCES OF NINE STARS IN THE r-PROCESS GALAXY RETICULUM II |
| title_fullStr | COMPLETE ELEMENT ABUNDANCES OF NINE STARS IN THE r-PROCESS GALAXY RETICULUM II |
| title_full_unstemmed | COMPLETE ELEMENT ABUNDANCES OF NINE STARS IN THE r-PROCESS GALAXY RETICULUM II |
| title_short | COMPLETE ELEMENT ABUNDANCES OF NINE STARS IN THE r-PROCESS GALAXY RETICULUM II |
| title_sort | complete element abundances of nine stars in the r process galaxy reticulum ii |
| url | http://hdl.handle.net/1721.1/108380 https://orcid.org/0000-0002-4863-8842 https://orcid.org/0000-0002-2139-7145 https://orcid.org/0000-0002-7155-679X |
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