Synthetic spectra to study multiple populations in Globular Clusters

Abstract

Spectroscopic and photometric studies have encountered evidence of multiple populations of stars in Galactic Globular Clusters. Anti-correlated C-N and O-Na abundance patterns in subsequent generations of cluster stars present new challenges to the fields of stellar nucleosynthesis and cluster evolution. In order to study extragalactic clusters, we modeled the integrated light of stellar populations with these typical abundances patterns and identified spectral indices that are sensitive to the light element anti-correlations. We are currently expanding the previous work to cover a larger wavelength range, using the low metallicity stars of the X-shooter Stellar Library for validation. Preliminary results confirm that cool low-gravity stars are the most difficult to model and indicate a decreasing quality-of-fit towards lower metallicities. This trend might be related to recent literature reports of mismatches between spectroscopic and photometric determinations of atmospheric parameters of low-Z giants.