New subgrouping of multiple stellar populations in NGC 2808 based on low-resolution spectroscopy

• Verfasst von: Hong, Seungsoo [VerfasserIn]
• Verfasst von: Lim, Dongwook [VerfasserIn]
• Verfasst von: Chung, Chul [VerfasserIn]
• Verfasst von: Kim, Jaeyeon [VerfasserIn]
• Verfasst von: Han, Sang-Il [VerfasserIn]
• Verfasst von: Lee, Young-Wook [VerfasserIn]
• Titel: New subgrouping of multiple stellar populations in NGC 2808 based on low-resolution spectroscopy
• Verf.angabe: Seungsoo Hong, Dongwook Lim, Chul Chung, Jaeyeon Kim, Sang-Il Han, and Young-Wook Lee
• E-Jahr: 2021
• Jahr: 2021 September 1
• Umfang: 11 S.
• Fussnoten: Gesehen am 02.11.2021
• Titel Quelle: Enthalten in: The astronomical journal
• Ort Quelle: London : Institute of Physics Publ., 1998
• Jahr Quelle: 2021
• Band/Heft Quelle: 162(2021), 4, Artikel-ID 130, Seite 1-11
• ISSN Quelle: 1538-3881
• DOI: doi:10.3847/1538-3881/ac0ce6
• Datenträger: Online-Ressource
• Sprache: eng
• K10plus-PPN: 1775857387

Abstract

We performed low-resolution spectroscopy for the red giant branch stars in an intriguing globular cluster (GC) NGC 2808, which hosts subpopulations with extreme helium and light-element abundances. In order to trace N, C, and Ca abundance differences among subpopulations, we measured CN, CH, and Ca ii H&K spectral indices, respectively. We identified four subpopulations (G1, G2, G3, and G4) from CN and CH strength, with CN-weak/CH-strong G1, CN-intermediate/CH-strong G2, CN-strong/CH-intermediate G3, and CN-strong/CH-weak G4. Compared to [Na/O] from high-resolution spectroscopy, we show that CN index can more clearly separate G1 and G2. Since CN traces N abundance in a GC, it implies that G1 and G2 would show a larger difference in [N/Fe] compared to [Na/Fe], as predicted by chemical evolution models. Later generation stars G3 and G4, however, are better separated with high-resolution spectroscopy. We also found that G4 shows a stronger Ca ii H&K line strength compared to that of G1, but we suspect this to be a result of unusually strong He enhancement and/or Mg depletion in G4 of this GC. This work illustrates that combining low- and high-resolution spectroscopic studies can improve the separation of subpopulations in GCs.