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

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

Arentsen, Anke
•
Starkenburg, Else
•
Aguado, David S.
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June 1, 2021
Monthly Notices Of The Royal Astronomical Society

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 ([C/Fe] >= +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 ([Fe/H] < -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(-13)(+14) per cent for stars with [Fe/H] < -3.0, and decreases to 16(-3)(+3) per cent for [Fe/H] < -2.5 and 5.7(-0.5)(+0.6) per cent for [Fe/H] < -2.0. The PIGS inner Galaxy CEMP fraction for [Fe/H] < -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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Type
research article
DOI
10.1093/mnras/stab1343
Web of Science ID

WOS:000767869100017

Author(s)
Arentsen, Anke
Starkenburg, Else
Aguado, David S.
Martin, Nicolas F.
Placco, Vinicius M.
Carlberg, Raymond
Gonzalez Hernandez, Jonay, I
Hill, Vanessa
Jablonka, Pascale  
Kordopatis, Georges
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Date Issued

2021-06-01

Publisher

OXFORD UNIV PRESS

Published in
Monthly Notices Of The Royal Astronomical Society
Volume

505

Issue

1

Start page

1239

End page

1253

Subjects

Astronomy & Astrophysics

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techniques: spectroscopic

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stars: carbon

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stars: chemically peculiar

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stars: population ii

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galaxy: bulge

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galaxy: formation

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follow-up observations

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red giant branch

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n-rich stars

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combs survey

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s-process

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milky

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metallicity

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halo

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discovery

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evolution

Editorial or Peer reviewed

REVIEWED

Written at

EPFL

EPFL units
LASTRO  
Available on Infoscience
March 28, 2022
Use this identifier to reference this record
https://infoscience.epfl.ch/handle/20.500.14299/186756
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