Heavy element abundances in Galactic Globular Clusters

TL;DR

This study analyzes heavy element abundances in 18 Galactic Globular Clusters using high-quality spectra to understand their chemical evolution and relation to the Galaxy's formation, revealing similarities with field stars and specific element correlations.

Contribution

It provides the largest uniform analysis of heavy element abundances in globular clusters, offering new insights into their chemical evolution and relation to Galactic formation.

Findings

Cu abundance shows no significant spread or correlation with Na.

Most GCs follow the chemical distribution of field stars.

Y abundance correlates mildly with Na in mid-metallicity GCs.

Abstract

Context. Globular clusters are considered key objects for understanding the formation and evolution of the Milky Way. In this sense, their characterisation in terms of their chemical and orbital parameters can provide constraints to the chemical evolution models of the Galaxy. Aims. We use the heavy element abundances of globular clusters to trace their overall behaviour in the Galaxy, aiming to analyse potential relations between the hot H-burning and s-process elements. Methods. We measured the content of Cu I and s- and r-process elements (Y II, Ba II, La II, and Eu II) in a sample of 210 giant stars in 18 Galactic Globular Clusters from high-quality UVES spectra. The clusters span a large metallicity range, and the sample is the largest uniformly analysed for what concerns heavy elements in Globular Clusters. Results. Cu abundances did not show considerable spread in the sample nor correlation with Na, meaning that the Na nucleosynthesis process does not affect the Cu abundance. Most GCs closely follow the Cu, Y, Ba, La, and Eu field stars' distribution, revealing a similar chemical evolution. The Y abundances in mid-metallicity regime GCs (-1.10 dex <[Fe/H]<-1.80 dex) display a mildly significant correlation with the Na abundance, which should be further investigated. Finally, we did not find any significant difference between the n-capture abundances among GCs with Galactic and extragalactic origin.