Dynamically tagged groups of metal-poor stars from the best and brightest survey
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2022
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Orbital characteristics based on Gaia Early Data Release 3 astrometric parameters are analyzed for ∼4000 metal poor stars ([Fe/H] −0.8) compiled from the Best and Brightest survey. Selected as metal-poor candidates based
on broadband near- and far-IR photometry, 43% of these stars had medium-resolution (1200 R 2000)
validation spectra obtained over a 7 yr campaign from 2014 to 2020 with a variety of telescopes. The remaining
stars were chosen based on photometric metallicity determinations from the Huang et al. recalibration of the Sky
Mapper Southern Survey. Dynamical clusters of these stars are obtained from the orbital energy and cylindrical
actions using the HDBSCAN unsupervised learning algorithm. We identify 52 dynamically tagged groups (DTGs)
with between five and 21 members; 18 DTGs have at least 10 member stars. Milky Way (MW) substructures such
as Gaia-Sausage-Enceladus, the Metal-Weak Thick-Disk, Thamnos, the Splashed Disk, and the Helmi Stream are
identified. Associations with MW globular clusters are determined for eight DTGs; no recognized MW dwarf
galaxies were associated with any of our DTGs. Previously identified dynamical groups are also associated with
our DTGs, with emphasis placed on their structural determination and possible new identifications. Chemically
peculiar stars are identified as members of several DTGs, with six DTGs that are associated with r-process enhanced stars. We demonstrate that the mean carbon and α-element abundances of our DTGs are correlated with
their mean metallicity in an understandable manner. Similarly, we find that the mean metallicity, carbon, and
α-element abundances are separable into different regions of the mean rotational-velocity space.
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SHANK, Derek et al. Dynamically tagged groups of metal-poor stars from the best and brightest survey. The Astrophysical Journal, Bristol, v. 926, n. 1, e22, 2022. DOI: 10.3847/1538-4357/ac409a. Disponível em: https://iopscience.iop.org/article/10.3847/1538-4357/ac409a. Acesso em: 11 maio 2023.