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Article Dans Une Revue Monthly Notices of the Royal Astronomical Society Année : 2021

The Pristine Inner Galaxy Survey (PIGS) III: carbon-enhanced metal-poor stars in the bulge

Anke Arentsen
Else Starkenburg
  • Fonction : Auteur
David Aguado
Nicolas Martin
Vinicius Placco
Raymond Carlberg
Jonay González hernández
  • Fonction : Auteur
Carmela Lardo
Lyudmila Mashonkina
Julio Navarro
  • Fonction : Auteur
Kim Venn
Sven Buder
  • Fonction : Auteur
Geraint Lewis
  • Fonction : Auteur
Zhen Wan
  • Fonction : Auteur
Daniel Zucker
  • Fonction : Auteur

Résumé

The most metal-deficient stars hold important clues about the early buildup and chemical evolution of the Milky Way, and carbon-enhanced metal-poor (CEMP) stars are of special interest. However, little is known about CEMP stars in the Galactic bulge. In this paper, we use the large spectroscopic sample of metal-poor stars from the Pristine Inner Galaxy Survey (PIGS) to identify CEMP stars ($\rm {[C/Fe]} \geqslant +0.7$) in the bulge region and to derive a CEMP fraction. We identify 96 new CEMP stars in the inner Galaxy, of which 62 are very metal-poor ($\rm {[Fe/H]} \lt -2.0$); this is more than a 10-fold increase compared to the seven previously known bulge CEMP stars. The cumulative fraction of CEMP stars in PIGS is $42^{\, +14\, }_{\, -13} {{\ \rm per\ cent}}$ for stars with $\rm {[Fe/H]} \lt -3.0$, and decreases to $16^{\, +3\, }_{\, -3} {{\ \rm per\ cent}}$ for $\rm {[Fe/H]} \lt -2.5$ and $5.7^{\, +0.6\, }_{\, -0.5} {{\ \rm per\ cent}}$ for $\rm {[Fe/H]} \lt -2.0$. The PIGS inner Galaxy CEMP fraction for $\rm {[Fe/H]} \lt -3.0$ is consistent with the halo fraction found in the literature, but at higher metallicities, the PIGS fraction is substantially lower. While this can partly be attributed to a photometric selection bias, such bias is unlikely to fully explain the low CEMP fraction at higher metallicities. Considering the typical carbon excesses and metallicity ranges for halo CEMP-s and CEMP-no stars, our results point to a possible deficiency of both CEMP-s and CEMP-no stars (especially the more metal-rich) in the inner Galaxy. The former is potentially related to a difference in the binary fraction, whereas the latter may be the result of a fast chemical enrichment in the early building blocks of the inner Galaxy.
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Dates et versions

hal-03337215 , version 1 (02-12-2022)

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Anke Arentsen, Else Starkenburg, David Aguado, Nicolas Martin, Vinicius Placco, et al.. The Pristine Inner Galaxy Survey (PIGS) III: carbon-enhanced metal-poor stars in the bulge. Monthly Notices of the Royal Astronomical Society, 2021, 505 (1), pp.1239-1253. ⟨10.1093/mnras/stab1343⟩. ⟨hal-03337215⟩
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