Deriving Metallicities From the Integrated Spectra of Extragalactic
  Globular Clusters Using the Near-Infrared Calcium Triplet
  The Ca triplet (CaT) feature in the near-infrared has been employed as a
metallicity indicator for individual stars as well as integrated light of
Galactic globular clusters (GCs) and galaxies with varying degrees of success,
and sometimes puzzling results. Using the DEIMOS multi-object spectrograph on
Keck we obtain a sample of 144 integrated light spectra of GCs around the
brightest group galaxy NGC 1407 to test whether the CaT index can be used as a
metallicity indicator for extragalactic GCs. Different sets of single stellar
population models make different predictions for the behavior of the CaT as a
function of metallicity. In this work, the metallicities of the GCs around NGC
1407 are obtained from CaT index values using an empirical conversion. The
measured CaT/metallicity distributions show unexpected features, the most
remarkable being that the brightest red and blue GCs have similar CaT values
despite their large difference in mean color. Suggested explanations for this
behavior in the NGC 1407 GC system are: 1) the CaT may be affected by a
population of hot blue stars, 2) the CaT may saturate earlier than predicted by
the models, and/or 3) color may not trace metallicity linearly. Until these
possibilities are understood, the use of the CaT as a metallicity indicator for
the integrated spectra of extragalactic GCs will remain problematic.
