WAGGS Globular Cluster Ca Triplet Metallicities

A major caveat of these studies is that the potential sensitivity to other stellar population parameters such as age, calcium abundance, and the initial mass function has not yet been empirically evaluated. Here, we present measurements of the strength of the CaT feature for 113 globular clusters in the Milky Way and its satellite galaxies.

We derive empirical calibrations between the CaT index and both the iron abundance ([Fe/H]) and calcium abundance ([Ca/H]), finding a tighter relationship for [Ca/H] than for [Fe/H]. For stellar populations, 3Gyr and older the CaT can be used to reliably measure [Ca/H] at the 0.1dex level but becomes less reliable for ages of ~2Gyr and younger. We find that the CaT is relatively insensitive to the horizontal branch morphology.