Stellar Population Astrophysics (SPA) with the TNG. alpha-elements, lithium, sodium and aluminum in 16 open clusters

TL;DR

This study provides a detailed chemical analysis of 16 open clusters in the Milky Way using high-resolution spectra, revealing abundance trends and comparing them with chemo-dynamical models to understand Galactic evolution.

Contribution

First homogeneous chemical characterization of 16 open clusters, including young and old, using high-resolution spectra and analysis of multiple elements.

Findings

Significant abundance gradients for [Mg/Fe] and [Ca/Fe] across clusters.

Good agreement between observed O and Mg abundances and models for intermediate and old clusters.

Sharp increase in element ratios among very young clusters, indicating model limitations.

Abstract

Exploring the Galactic chemical evolution and enrichment scenarios with open clusters allows us to understand the history of the Milky Way disk. High-resolution spectra of OCs are a crucial tool, as they provide precise chemical information, to combine with precise distances and ages. The aim of the Stellar Population Astrophysics project is to derive homogeneous and accurate comprehensive chemical characterization of a number of poorly studied OCs.Using the HARPS-N echelle spectrograph at the Telescopio Nazionale Galileo, we obtained high-resolution spectra of giant stars in 18 OCs, 16 of which are chemically characterized for the first time, and two of which are well studied for comparison. The OCs in this sample have ages from a few tens of Myr to 4 Gyr, with a prevalence of young clusters. We already presented the radial velocities and atmospheric parameters for them in a previous SPA paper. Here, we present results for the alpha-elements O, and the light elements, all determined by the equivalent width method. We also measured Li abundance through the synthesis method.We discuss the behaviors of lithium, sodium and aluminum in the context of stellar evolution. We study the radial, vertical, and age trends for the measured abundance ratios in a sample that combines our results and recent literature for OCs, finding significant gradients only for [Mg/Fe] and [Ca/Fe] in all cases. Finally,we compare O and Mg in the combined sample with chemo-dynamical models, finding a good agreement for intermediate-age and old clusters. There is a sharp increase in the abundance ratios measured among very young clusters, accompanied by a poorer fit with the models for O and Mg, likely related to the inadequacy of traditional model atmospheres and methods in the derivation of atmospheric parameters and abundance ratios for stars of such young ages