Optimal Integrated Abundances for Chemical Tagging of Extragalactic Globular Clusters

Abstract

High resolution integrated light (IL) spectroscopy provides detailed abundances of distant globular clusters whose stars cannot be resolved. Abundance comparisons with other systems (e.g. for chemical tagging) require understanding the systematic offsets that can occur between clusters, such as those due to uncertainties in the underlying stellar population. This paper analyses high resolution IL spectra of the Galactic globular clusters 47 Tuc, M3, M13, NGC 7006, and M15 to (1) quantify potential systematic uncertainties in Fe, Ca, Ti, Ni, Ba, and Eu and (2) identify the most stable abundance ratios that will be useful in future analyses of unresolved targets. When stellar populations are well-modelled, uncertainties are ~0.1-0.2 dex based on sensitivities to the atmospheric parameters alone; in the worst case scenarios, uncertainties can rise to 0.2-0.4 dex. The [Ca I/Fe I] ratio is identified as the optimal integrated [alpha/Fe] indicator (with offsets <0.1 dex), while [Ni I/Fe I] is also extremely stable to within <0.1 dex. The [Ba II/Eu II] ratios are also stable when the underlying populations are well modelled and may also be useful for chemical tagging.

28 pages, 4 figures, accepted for publication in the Monthly Notices of the Royal Astronomical Society

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Cited by in corpus (12)

• Final Targeting Strategy for the SDSS-IV APOGEE-2N Survey
• The Detailed Chemical Properties of M31 Star Clusters I. Fe, Alpha and Light Elements
• Integrated Light Chemical Tagging Analyses of Seven M31 Outer Halo Globular Clusters from the Pan-Andromeda Archaeological Survey
• The chemical composition of globular clusters in the Local Group
• Infrared High-Resolution Integrated Light Spectral Analyses of M31 Globular Clusters from APOGEE
• Globular Cluster Abundances from High-Resolution, Integrated-Light Spectroscopy. II. Expanding the Metallicity Range for Old Clusters and Updated Analysis Techniques
• The Massive M31 Cluster G1: Detailed Chemical Abundances from Integrated Light Spectroscopy
• Metallicities of Outer Halo M31 Globular Clusters from Integrated Light Calcium-II Triplet Spectroscopy
• Integrated Spectra of Milky Way Globular Cluster
• Synthetic stellar spectra to study multiple populations in globular clusters: an extended grid and the effects on the integrated light
• Study of Integrated Spectra of Four Globular Clusters in M31
• Chemical Abundances of Seven Outer Halo M31 Globular Clusters from the Pan-Andromeda Archaeological Survey