Search for Extremely Metal-poor Stars with Gemini-N/Graces. I. Chemical-abundance Analysis
We present stellar parameters and abundances of 13 elements for 18 very metal-poor (VMP; [Fe/H] < –2.0) stars, selected as extremely metal-poor (EMP; [Fe/H] < –3.0) candidates from the Sloan Digital Sky Survey and Large sky Area Multi-Object Fiber Spectroscopic Telescope survey. High-resolutio...
| Main Authors: | , , , , , , , |
|---|---|
| Format: | Article |
| Language: | English |
| Published: |
IOP Publishing
2023-01-01
|
| Series: | The Astrophysical Journal |
| Subjects: | |
| Online Access: | https://doi.org/10.3847/1538-4357/acc58a |
| _version_ | 1827357786895286272 |
|---|---|
| author | Miji Jeong Young Sun Lee Timothy C. Beers Vinicius M. Placco Young Kwang Kim Jae-Rim Koo Ho-Gyu Lee Soung-Chul Yang |
| author_facet | Miji Jeong Young Sun Lee Timothy C. Beers Vinicius M. Placco Young Kwang Kim Jae-Rim Koo Ho-Gyu Lee Soung-Chul Yang |
| author_sort | Miji Jeong |
| collection | DOAJ |
| description | We present stellar parameters and abundances of 13 elements for 18 very metal-poor (VMP; [Fe/H] < –2.0) stars, selected as extremely metal-poor (EMP; [Fe/H] < –3.0) candidates from the Sloan Digital Sky Survey and Large sky Area Multi-Object Fiber Spectroscopic Telescope survey. High-resolution spectroscopic observations were performed using GEMINI-N/GRACES. We find 10 EMP stars among our candidates, and we newly identify three carbon-enhanced metal-poor stars with [Ba/Fe] < 0. Although chemical abundances of our VMP/EMP stars generally follow the overall trend of other Galactic halo stars, there are a few exceptions. One Na-rich star ([Na/Fe] = +1.14) with low [Mg/Fe] suggests a possible chemical connection with second-generation stars in a globular cluster. The progenitor of an extremely Na-poor star ([Na/Fe] = –1.02) with high K- and Ni-abundance ratios may have undergone a distinct nucleosynthesis episode, associated with core-collapse supernovae (SNe) having a high explosion energy. We have also found a Mg-rich star ([Mg/Fe] = +0.73) with slightly enhanced Na and extremely low [Ba/Fe], indicating that its origin is not associated with neutron-capture events. On the other hand, the origin of the lowest Mg abundance ([Mg/Fe] = –0.61) star could be explained by accretion from a dwarf galaxy, or formation in a gas cloud largely polluted by SNe Ia. We have also explored the progenitor masses of our EMP stars by comparing their chemical-abundance patterns with those predicted by Population III SNe models, and find a mass range of 10–26 M _⊙ , suggesting that such stars were primarily responsible for the chemical enrichment of the early Milky Way. |
| first_indexed | 2024-03-08T05:53:02Z |
| format | Article |
| id | doaj.art-cf7c41e88e7b4ba38de38fdf18a4ce10 |
| institution | Directory Open Access Journal |
| issn | 1538-4357 |
| language | English |
| last_indexed | 2024-03-08T05:53:02Z |
| publishDate | 2023-01-01 |
| publisher | IOP Publishing |
| record_format | Article |
| series | The Astrophysical Journal |
| spelling | doaj.art-cf7c41e88e7b4ba38de38fdf18a4ce102024-02-05T08:30:30ZengIOP PublishingThe Astrophysical Journal1538-43572023-01-0194813810.3847/1538-4357/acc58aSearch for Extremely Metal-poor Stars with Gemini-N/Graces. I. Chemical-abundance AnalysisMiji Jeong0Young Sun Lee1https://orcid.org/0000-0001-5297-4518Timothy C. Beers2https://orcid.org/0000-0003-4573-6233Vinicius M. Placco3https://orcid.org/0000-0003-4479-1265Young Kwang Kim4https://orcid.org/0000-0002-6411-5857Jae-Rim Koo5https://orcid.org/0000-0001-8969-0009Ho-Gyu Lee6Soung-Chul Yang7https://orcid.org/0000-0001-9842-639XDepartment of Astronomy, Space Science, and Geology, Chungnam National University , Daejeon 34134, Republic of KoreaDepartment of Astronomy and Space Science, Chungnam National University , Daejeon 34134, Republic of Korea ; youngsun@cnu.ac.kr; Department of Physics and Astronomy and JINA Center for the Evolution of the Elements, University of Notre Dame , IN 46556, USADepartment of Physics and Astronomy and JINA Center for the Evolution of the Elements, University of Notre Dame , IN 46556, USANSF’s NOIRLab, 950 N. Cherry Avenue, Tucson, AZ 85719, USADepartment of Astronomy and Space Science, Chungnam National University , Daejeon 34134, Republic of Korea ; youngsun@cnu.ac.krDepartment of Earth Science Education, Kongju National University , 56 Gongjudaehak-ro, Gongju-si, Chungcheongnam-do 32588, Republic of KoreaKorea Astronomy and Space Science Institute , Daejeon 34055, Republic of KoreaKorea Astronomy and Space Science Institute , Daejeon 34055, Republic of KoreaWe present stellar parameters and abundances of 13 elements for 18 very metal-poor (VMP; [Fe/H] < –2.0) stars, selected as extremely metal-poor (EMP; [Fe/H] < –3.0) candidates from the Sloan Digital Sky Survey and Large sky Area Multi-Object Fiber Spectroscopic Telescope survey. High-resolution spectroscopic observations were performed using GEMINI-N/GRACES. We find 10 EMP stars among our candidates, and we newly identify three carbon-enhanced metal-poor stars with [Ba/Fe] < 0. Although chemical abundances of our VMP/EMP stars generally follow the overall trend of other Galactic halo stars, there are a few exceptions. One Na-rich star ([Na/Fe] = +1.14) with low [Mg/Fe] suggests a possible chemical connection with second-generation stars in a globular cluster. The progenitor of an extremely Na-poor star ([Na/Fe] = –1.02) with high K- and Ni-abundance ratios may have undergone a distinct nucleosynthesis episode, associated with core-collapse supernovae (SNe) having a high explosion energy. We have also found a Mg-rich star ([Mg/Fe] = +0.73) with slightly enhanced Na and extremely low [Ba/Fe], indicating that its origin is not associated with neutron-capture events. On the other hand, the origin of the lowest Mg abundance ([Mg/Fe] = –0.61) star could be explained by accretion from a dwarf galaxy, or formation in a gas cloud largely polluted by SNe Ia. We have also explored the progenitor masses of our EMP stars by comparing their chemical-abundance patterns with those predicted by Population III SNe models, and find a mass range of 10–26 M _⊙ , suggesting that such stars were primarily responsible for the chemical enrichment of the early Milky Way.https://doi.org/10.3847/1538-4357/acc58aChemical abundancesGalaxy chemical evolutionMilky Way GalaxyInterstellar abundancesGalaxy stellar content |
| spellingShingle | Miji Jeong Young Sun Lee Timothy C. Beers Vinicius M. Placco Young Kwang Kim Jae-Rim Koo Ho-Gyu Lee Soung-Chul Yang Search for Extremely Metal-poor Stars with Gemini-N/Graces. I. Chemical-abundance Analysis The Astrophysical Journal Chemical abundances Galaxy chemical evolution Milky Way Galaxy Interstellar abundances Galaxy stellar content |
| title | Search for Extremely Metal-poor Stars with Gemini-N/Graces. I. Chemical-abundance Analysis |
| title_full | Search for Extremely Metal-poor Stars with Gemini-N/Graces. I. Chemical-abundance Analysis |
| title_fullStr | Search for Extremely Metal-poor Stars with Gemini-N/Graces. I. Chemical-abundance Analysis |
| title_full_unstemmed | Search for Extremely Metal-poor Stars with Gemini-N/Graces. I. Chemical-abundance Analysis |
| title_short | Search for Extremely Metal-poor Stars with Gemini-N/Graces. I. Chemical-abundance Analysis |
| title_sort | search for extremely metal poor stars with gemini n graces i chemical abundance analysis |
| topic | Chemical abundances Galaxy chemical evolution Milky Way Galaxy Interstellar abundances Galaxy stellar content |
| url | https://doi.org/10.3847/1538-4357/acc58a |
| work_keys_str_mv | AT mijijeong searchforextremelymetalpoorstarswithgeminingracesichemicalabundanceanalysis AT youngsunlee searchforextremelymetalpoorstarswithgeminingracesichemicalabundanceanalysis AT timothycbeers searchforextremelymetalpoorstarswithgeminingracesichemicalabundanceanalysis AT viniciusmplacco searchforextremelymetalpoorstarswithgeminingracesichemicalabundanceanalysis AT youngkwangkim searchforextremelymetalpoorstarswithgeminingracesichemicalabundanceanalysis AT jaerimkoo searchforextremelymetalpoorstarswithgeminingracesichemicalabundanceanalysis AT hogyulee searchforextremelymetalpoorstarswithgeminingracesichemicalabundanceanalysis AT soungchulyang searchforextremelymetalpoorstarswithgeminingracesichemicalabundanceanalysis |