Chemical Doppelgangers in GALAH DR3: the Distinguishing Power of Neutron-Capture Elements Among Milky Way Disk Stars

Catherine Manea, Keith Hawkins, Melissa K. Ness, Sven Buder, Sarah L. Martell, Daniel B. Zucker

Research output: Contribution to journalArticlepeer-review

Abstract

The observed chemical diversity of Milky Way stars places important constraints on Galactic chemical
evolution and the mixing processes that operate within the interstellar medium. Recent works have found that
the chemical diversity of disk stars is low. For example, the APOGEE "chemical doppelganger rate,” or the
rate at which random pairs of field stars appear as chemically similar as stars born together, is high, and the
chemical distributions of APOGEE stars in some Galactic populations are well-described by two-dimensional
models. However, limited attention has been paid to the heavy elements (Z > 30) in this context. In this work, we
probe the potential for neutron-capture elements to enhance the chemical diversity of stars by determining their
effect on the chemical doppelganger rate. We measure the doppelganger rate in GALAH DR3, with abundances
rederived using The Cannon, and find that considering the neutron-capture elements decreases the doppelganger
rate from ∼2.2% to 0.4%, nearly a factor of 6, for stars with-0.1 < [Fe/H] < 0.1. While chemical similarity
correlates with similarity in age and dynamics, including neutron-capture elements does not appear to select
stars that are more similar in these characteristics. Our results highlight that the neutron-capture elements
contain information that is distinct from that of the lighter elements and thus add at least one dimension to Milky
Way abundance space. This work illustrates the importance of considering the neutron-capture elements when
chemically characterizing stars and motivates ongoing work to improve their atomic data and measurements in
spectroscopic surveys.
Original languageEnglish
Number of pages23
JournalarXiv e-prints
DOIs
Publication statusSubmitted - 23 Oct 2023

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