Searching for GC-like abundance patterns in young massive clusters

TL;DR

This study investigates whether young massive clusters (YMCs) exhibit the globular cluster-like abundance patterns, specifically in light elements, by analyzing their integrated spectra and comparing them to field RSGs.

Contribution

The paper provides the first differential abundance analysis of YMCs' integrated spectra, finding no evidence of extreme Al enhancements typical of GCs.

Findings

No extreme [Al/Fe] enhancements similar to GCs detected

Small abundance variations cannot be ruled out

Supports the idea that YMCs may lack multiple populations like GCs

Abstract

Studies during the last decade have revealed that nearly all Globular Clusters (GCs) host multiple populations (MPs) of stars with a distinctive chemical patterns in light elements. No evidence of such MPs has been found so far in lower-mass ($< \sim 10^4$ M$_{\odot}$) open clusters nor in intermediate age (1-2 Gyr) massive ($> 10^5$ M$_{\odot}$) clusters in the Local Group. Young massive clusters (YMCs) have masses and densities similar to those expected of young GCs in the early universe, and their near-infrared (NIR) spectra are dominated by the light of red super giants (RSGs). The spectra of these stars may be used to determine the cluster's abundances, even though the individual stars cannot be spatially resolved from one another. We carry out a differential analysis between the Al lines of YMC NGC 1705: 1 and field Small Magellanic Cloud RSGs with similar metallicities. We exclude at high confidence extreme [Al/Fe] enhancements similar to those observed in GCs like NGC 2808 or NGC 6752. However, smaller variations cannot be excluded.