A baseline on the relation between chemical patterns and birth stellar cluster

TL;DR

This study evaluates the potential of chemical tagging to identify stars born together by analyzing APOGEE data with machine learning, revealing significant challenges and the importance of additional information like stellar ages.

Contribution

It demonstrates that chemical abundances alone are insufficient for reliable star cluster recovery, highlighting the limitations of strong chemical tagging.

Findings

Open clusters can be recovered with ~75% accuracy using machine learning.

Prediction accuracy is mainly affected by chemical abundance uncertainties.

Performance decreases when field stars outnumber cluster members.

Abstract

The chemical composition of a star's atmosphere reflects the chemical composition of its birth environment. Therefore, it should be feasible to recognize stars born together that have scattered throughout the galaxy, solely based on their chemistry. This concept, known as "strong chemical tagging", is a major objective of spectroscopic studies, but has yet to yield the anticipated results. We assess the existence and the robustness of the relation between chemical abundances and birth place using known member stars of open clusters. We followed a supervised machine learning approach, using chemical abundances obtained from APOGEE DR17, observed open clusters as labels and different data preprocessing techniques. We found that open clusters can be recovered with any classifier and on data whose features are not carefully selected. In the sample with no field stars, we obtain an average accuracy of $75.2\%$ and we find that the prediction accuracy depends mostly on the uncertainties of the chemical abundances. When field stars outnumber the cluster members, the performance degrades. Our results show the difficulty of recovering birth clusters using chemistry alone, even in a supervised scenario. This clearly challenges the feasibility of strong chemical tagging. Nevertheless, including information about ages could potentially enhance the possibility of recovering birth clusters.