The Ca II triplet in red giant spectra: [Fe/H] determinations and the role of [Ca/Fe]
Date
2016
Authors
Da Costa, Gary
Journal Title
Journal ISSN
Volume Title
Publisher
Blackwell Publishing Ltd
Abstract
Measurements are presented and analysed of the strength of the Ca II triplet lines in red giants in Galactic globular and open clusters, and in a sample of red giants in the LMC disc that have significantly different [Ca/Fe] abundance ratios to the Galactic objects. The Galactic objects are used to generate a calibration between Ca II triplet line strength and [Fe/H], which is then used to estimate [Fe/H]CaT for the LMC stars. The values are then compared with the [Fe/H]spec determinations from high-dispersion spectroscopy. After allowance for a small systematic offset, the two abundance determinations are in excellent agreement. Further, as found in earlier studies, the difference is only a very weak function of the [Ca/Fe] ratio. For example, changing [Ca/Fe] from +0.3 to −0.2 causes the Ca II-based abundance to underestimate [Fe/H]spec by only ∼0.15 dex, assuming a Galactic calibration. Consequently, the Ca II triplet approach to metallicity determinations can be used without significant bias to study stellar systems that have substantially different chemical evolution histories.
Description
Keywords
Citation
Collections
Source
Monthly Notices of the Royal Astronomical Society
Type
Journal article
Book Title
Entity type
Access Statement
Open Access