Medium resolution spectroscopy and chemical composition of Galactic globular clusters

TL;DR

This study employs medium-resolution integrated-light spectra and stellar atmosphere models to determine the chemical composition and age of six Galactic globular clusters, enhancing stellar population analysis methods.

Contribution

It introduces a novel approach combining spectral fitting and isochrone-based stellar parameters to derive cluster properties from medium-resolution spectra.

Findings

Good agreement with literature on chemical composition and age

Method effectively determines element abundances and ages

Potential for application to extragalactic star clusters

Abstract

We used integrated-light medium-resolution spectra of six Galactic globular clusters and model stellar atmospheres to carry out population synthesis and to derive chemical composition and age of the clusters. We used medium-resolution spectra of globular clusters published by Schiavon et al. (2005), as well as our long-slit observations with the 1.93 m telescope of the Haute Provence Observatory. The observed spectra were fitted to the theoretical ones interactively. As an initial approach, we used masses, radii and log g of stars in the clusters corresponding to the best fitting isochrones in the observed color-magnitude diagrams. The computed synthetic blanketed spectra of stars were summed according to the Chabrier mass function. To improve the determination of age and helium content, the shape and depth of the Balmer absorption lines was analysed. The abundances of Mg, Ca, C and several other elements were derived. A reasonable agreement with the literature data both in chemical composition and in age of the clusters is found. Our method might be useful for the development of stellar population models and for a better understanding of extragalactic star clusters.