Strong Chemical Tagging in FIRE: Intra and Inter-Cluster Chemical Homogeneity in Open Clusters in Milky Way-like Galaxy Simulations

TL;DR

This study assesses the feasibility of strong chemical tagging in open star clusters using FIRE-2 galaxy simulations, finding that elemental abundances lack sufficient uniqueness to reliably identify cluster membership.

Contribution

It provides a detailed comparison of intra- and inter-cluster chemical homogeneity in simulations and observations, highlighting limitations of chemical tagging for cluster identification.

Findings

Intra-cluster abundance scatter is minimal (<0.020 dex).

Different clusters have similar mean abundance patterns.

Elemental abundances are insufficient for reliable cluster membership identification.

Abstract

Open star clusters are the essential building blocks of the Galactic disk; "strong chemical tagging" - the premise that all star clusters can be reconstructed given chemistry information alone - is a driving force behind many current and upcoming large Galactic spectroscopic surveys. In this work, we characterize abundance patterns for 9 elements (C, N, O, Ne, Mg, Si, S, Ca, and Fe) in open clusters (OCs) in three galaxies (m12i, m12f, and m12m) from the Latte suite of FIRE-2 simulations to investigate if strong chemical tagging is possible in these simulations. We select young massive (>=10^(4.6) Msun) OCs formed in the last ~100 Myr and calculate the intra- and inter-cluster abundance scatter for these clusters. We compare these results with analogous calculations drawn from observations of OCs in the Milky Way. We find the intra-cluster scatter of the observations and simulations to be comparable. While the abundance scatter within each cluster is minimal (<0.020 dex), the mean abundance patterns of different clusters are not unique. We also calculate the chemical difference in intra- and inter-cluster star pairs and find it, in general, to be so small that it is difficult to distinguish between stars drawn from the same OC or from different OCs. Despite tracing three distinct nucleosynthetic families (core-collapse supernovae, white dwarf supernovae, and stellar winds), we conclude that these elemental abundances do not provide enough discriminating information to use strong chemical tagging for reliable OC membership.