The near-infrared Ca II triplet as a metallicity indicator - II. Extension to extremely metal-poor metallicity regimes

Carrera, R.; Pancino, E.; Gallart, C.; del Pino, A.
Bibliographical reference

Monthly Notices of the Royal Astronomical Society, Volume 434, Issue 2, p.1681-1691

Advertised on:
9
2013
Number of authors
4
IAC number of authors
3
Citations
79
Refereed citations
72
Description
We extend our previous calibration of the infrared Ca II triplet (CaT) as a metallicity indicator to the metal-poor regime by including observations of 55 field stars with [Fe/H] down to -4.0 dex. While we previously solved the saturation at high metallicity using a combination of a Lorentzian and a Gaussian to reproduce the line profiles, in this paper we address the non-linearity at low metallicity following the suggestion of Starkenburg et al. of adding two non-linear terms to the relation among the [Fe/H], luminosity and strength of the calcium triplet lines. Our calibration thus extends from -4.0 to +0.5 in metallicity and is presented using four different luminosity indicators: V - VHB, MV, MI and MK. The calibration obtained in this paper results in a tight correlation between [Fe/H] abundances measured from high-resolution spectra and [Fe/H] values derived from the CaT, over the whole metallicity range covered.
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