Kavli Affiliate: Anna Frebel
| First 5 Authors: Derek Shank, Timothy C. Beers, Vinicius M. Placco, Dmitrii Gudin, Thomas Catapano
| Summary:
Orbital characteristics based on Gaia Early Data Release 3 astrometric
parameters are analyzed for ${sim} 1700$ $r$-process-enhanced (RPE; [Eu/Fe] $>
+0.3$) metal-poor stars ([Fe/H] $leq -0.8$) compiled from the $R$-Process
Alliance, the GALactic Archaeology with HERMES (GALAH) DR3 survey, and
additional literature sources. We find dynamical clusters of these stars based
on their orbital energies and cylindrical actions using the HDBSCAN
~unsupervised learning algorithm. We identify $36$ Chemo-Dynamically Tagged
Groups (CDTGs) containing between $5$ and $22$ members; $17$ CDTGs have at
least $10$ member stars. Previously known Milky Way (MW) substructures such as
Gaia-Sausage-Enceladus, the Splashed Disk, the Metal-Weak Thick Disk, the Helmi
Stream, LMS-1 (Wukong), and Thamnos are re-identified. Associations with MW
globular clusters are determined for $7$ CDTGs; no recognized MW dwarf galaxy
satellites were associated with any of our CDTGs. Previously identified
dynamical groups are also associated with our CDTGs, adding structural
determination information and possible new identifications. Carbon-Enhanced
Metal-Poor RPE (CEMP-$r$) stars are identified among the targets; we assign
these to morphological groups in the Yoon-Beers $A$(C)$_{c}$ vs. [Fe/H]
Diagram. Our results confirm previous dynamical analyses that showed RPE stars
in CDTGs share common chemical histories, influenced by their birth
environments.
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