Targeting bright metal-poor stars in the disk and halo systems of the galaxy
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2021
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We present the results of spectroscopic follow-up for 1897 low-metallicity star candidates, selected from the Best
& Brightest (B&B) Survey, carried out with the GMOS-N/S (Gemini North/South telescopes) and Goodman
(SOAR Telescope) spectrographs. From these low-resolution (R ∼ 2000) spectra, we estimate stellar atmospheric
parameters, as well as carbon and magnesium abundance ratios. We confirm that 56% of our program stars are
metal-poor ([Fe/H] < − 1.0), 30% are very metal-poor (VMP; [Fe/H] < − 2.0), and 2% are extremely metal-poor
(EMP; [Fe/H] < − 3.0). There are 191 carbon-enhanced metal-poor (CEMP) stars, resulting in CEMP fractions of
19% and 43% for the VMP and EMP regimes, respectively. A total of 94 confirmed CEMP stars belong to Group I
(A(C) 7.25) and 97 to Group II (A(C) 7.25) in the Yoon–Beers A(C)−[Fe/H] diagram. Moreover, we combine
these data with Gaia EDR3 astrometric information to delineate new target-selection criteria, which have been
applied to the Goodman/SOAR candidates, to more than double the efficiency for identification of bona fide VMP
and EMP stars in comparison to random draws from the B&B catalog. We demonstrate that this target-selection
approach can achieve success rates of 96%, 76%, 28%, and 4% for [Fe/H] − 1.5, − 2.0, − 2.5 and − 3.0,
respectively. Finally, we investigate the presence of dynamically interesting stars in our sample. We find that
several VMP/EMP ([Fe/H] − 2.5) stars can be associated with either the disk system or halo substructures like
Gaia-Sausage/Enceladus and Sequoia.
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LIMBERG, Guilherme et al. Targeting bright metal-poor stars in the disk and halo systems of the galaxy. The Astrophysical Journal, Bristol, v. 913, n. 1, e11, 2021. DOI: 10.3847/1538-4357/abeefe. Disponível em: https://iopscience.iop.org/article/10.3847/1538-4357/abeefe. Acesso em: 11 maio 2023.