A Comprehensive Study of Open Cluster Chemical Homogeneity using APOGEE and Milky Way Mapper Abundances

TL;DR

This study assesses the chemical homogeneity of open clusters using APOGEE and Milky Way Mapper data, finding most elements are highly homogeneous within 0.02 dex, with some exceptions for neutron capture and weak-line elements.

Contribution

It provides the first comprehensive quantification of chemical homogeneity across multiple elements in open clusters using large spectroscopic surveys.

Findings

Most elements are homogeneous within 0.02 dex in open clusters.

Neutron capture and weak-line elements show larger heterogeneity, up to 0.2 dex.

Giant stars in clusters are slightly more homogeneous than field stars.

Abstract

Stars in an open cluster are assumed to have formed from a broadly homogeneous distribution of gas, implying that they should be chemically homogeneous. Quantifying the level to which open clusters are chemically homogeneous can therefore tell us about ISM pollution and gas-mixing in progenitor molecular clouds. Using SDSS-V Milky Way Mapper and SDSS-IV APOGEE DR17 abundances, we test this assumption by quantifying intrinsic chemical scatter in up to 20 different chemical abundances across 26 Milky Way open clusters. We find that we can place 3${\sigma}$ upper limits on open cluster homogeneity within 0.02 dex or less in the majority of elements, while for neutron capture elements, as well as those elements having weak lines, we place limits on their homogeneity within 0.2 dex. Finally, we find that giant stars in open clusters are ~0.01 dex more homogeneous than a matched sample of field stars.