Comparison of the Chemical Compositions between the Bright and Faint Red Clumps for the Metal-poor and Metal-rich Populations in the Milky Way Bulge
We examined the double red clump (RC) observed in the Galactic bulge, interpreted as a difference in distance (“X-shaped bulge scenario”) or in chemical composition (“multiple population scenario”). To verify chemical differences between the RC groups, we performed low-resolution spectroscopy for RC...
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2024-01-01
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| author | Seungsoo Hong Dongwook Lim Young-Wook Lee |
| author_facet | Seungsoo Hong Dongwook Lim Young-Wook Lee |
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| description | We examined the double red clump (RC) observed in the Galactic bulge, interpreted as a difference in distance (“X-shaped bulge scenario”) or in chemical composition (“multiple population scenario”). To verify chemical differences between the RC groups, we performed low-resolution spectroscopy for RC and red giant branch (RGB) stars using Gemini-South/GMOS in three fields of the bulge and collected diverse data from the literature. We divided our sample stars not only into bright RC (bRC) and faint RC (fRC) groups, but also into bluer ([Fe/H] < −0.1) and redder ([Fe/H] > −0.1) groups following recent u -band photometric studies. For the metal-poor stars, no statistically significant difference in the CN index was detected between the bright and faint RC groups for all observed fields. However, we found, from crossmatching with high-resolution spectroscopic data, a sign of Na enhancement in the “metal-poor and bright” RC group compared to the “metal-poor and faint” group at ( l , b ) = (−1°, −8.°5). When the contributions of the RGB stars on the RC regimes are taken into account, the Na abundance difference between genuine RCs would correspond to Δ[Na/Fe] ≃ 0.23 dex, similar to a globular cluster (GC) with multiple populations. In contrast, the metal-rich stars do not show chemical differences between the bright and faint RC groups. This implies that the double RC observed in the metal-poor component of the bulge might be linked to the multiple populations originating from GC-like subsystems, whereas that of the metal-rich component would have been produced by the X-shaped structure. Our results support previous studies suggesting the composite nature of the Milky Way bulge. |
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| language | English |
| publishDate | 2024-01-01 |
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| series | The Astrophysical Journal |
| spelling | doaj-art-ea097ede99164e9dbe6c9f551deb8aac2025-08-20T02:19:51ZengIOP PublishingThe Astrophysical Journal1538-43572024-01-0197717110.3847/1538-4357/ad8a5eComparison of the Chemical Compositions between the Bright and Faint Red Clumps for the Metal-poor and Metal-rich Populations in the Milky Way BulgeSeungsoo Hong0https://orcid.org/0000-0003-4364-6744Dongwook Lim1https://orcid.org/0000-0001-7277-7175Young-Wook Lee2https://orcid.org/0000-0002-2210-1238Institute for Data Innovation in Science & Department of Physics and Astronomy, Seoul National Universit y, Seoul 08826, Republic of Korea; Center for Galaxy Evolution Research & Department of Astronomy, Yonsei University , Seoul 03722, Republic of Korea ; ywlee2@yonsei.ac.kr; SNU Astronomy Research Center, Seoul National University , Seoul 08826, Republic of KoreaCenter for Galaxy Evolution Research & Department of Astronomy, Yonsei University , Seoul 03722, Republic of Korea ; ywlee2@yonsei.ac.krCenter for Galaxy Evolution Research & Department of Astronomy, Yonsei University , Seoul 03722, Republic of Korea ; ywlee2@yonsei.ac.krWe examined the double red clump (RC) observed in the Galactic bulge, interpreted as a difference in distance (“X-shaped bulge scenario”) or in chemical composition (“multiple population scenario”). To verify chemical differences between the RC groups, we performed low-resolution spectroscopy for RC and red giant branch (RGB) stars using Gemini-South/GMOS in three fields of the bulge and collected diverse data from the literature. We divided our sample stars not only into bright RC (bRC) and faint RC (fRC) groups, but also into bluer ([Fe/H] < −0.1) and redder ([Fe/H] > −0.1) groups following recent u -band photometric studies. For the metal-poor stars, no statistically significant difference in the CN index was detected between the bright and faint RC groups for all observed fields. However, we found, from crossmatching with high-resolution spectroscopic data, a sign of Na enhancement in the “metal-poor and bright” RC group compared to the “metal-poor and faint” group at ( l , b ) = (−1°, −8.°5). When the contributions of the RGB stars on the RC regimes are taken into account, the Na abundance difference between genuine RCs would correspond to Δ[Na/Fe] ≃ 0.23 dex, similar to a globular cluster (GC) with multiple populations. In contrast, the metal-rich stars do not show chemical differences between the bright and faint RC groups. This implies that the double RC observed in the metal-poor component of the bulge might be linked to the multiple populations originating from GC-like subsystems, whereas that of the metal-rich component would have been produced by the X-shaped structure. Our results support previous studies suggesting the composite nature of the Milky Way bulge.https://doi.org/10.3847/1538-4357/ad8a5eMilky Way formationGlobular star clustersGalactic bulgeRed giant clumpSpectroscopyStellar populations |
| spellingShingle | Seungsoo Hong Dongwook Lim Young-Wook Lee Comparison of the Chemical Compositions between the Bright and Faint Red Clumps for the Metal-poor and Metal-rich Populations in the Milky Way Bulge The Astrophysical Journal Milky Way formation Globular star clusters Galactic bulge Red giant clump Spectroscopy Stellar populations |
| title | Comparison of the Chemical Compositions between the Bright and Faint Red Clumps for the Metal-poor and Metal-rich Populations in the Milky Way Bulge |
| title_full | Comparison of the Chemical Compositions between the Bright and Faint Red Clumps for the Metal-poor and Metal-rich Populations in the Milky Way Bulge |
| title_fullStr | Comparison of the Chemical Compositions between the Bright and Faint Red Clumps for the Metal-poor and Metal-rich Populations in the Milky Way Bulge |
| title_full_unstemmed | Comparison of the Chemical Compositions between the Bright and Faint Red Clumps for the Metal-poor and Metal-rich Populations in the Milky Way Bulge |
| title_short | Comparison of the Chemical Compositions between the Bright and Faint Red Clumps for the Metal-poor and Metal-rich Populations in the Milky Way Bulge |
| title_sort | comparison of the chemical compositions between the bright and faint red clumps for the metal poor and metal rich populations in the milky way bulge |
| topic | Milky Way formation Globular star clusters Galactic bulge Red giant clump Spectroscopy Stellar populations |
| url | https://doi.org/10.3847/1538-4357/ad8a5e |
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