Globular clusters of NGC 3115 in the near-infrared. Demonstrating the
  correctness of two opposing scenarios
  We combined new near-infrared VLT/HAWK-I data of the globular clusters (GCs)
in the isolated edge-on S0 galaxy NGC 3115 with optical and spectroscopic ones
taken from the literature, with the aim of analyzing the multiband GC color
distributions. A recent study from the SLUGGS survey has shown that the GCs in
this galaxy follow a bimodal distribution of Ca II triplet indices. Thus, NGC
3115 presents a critical example of a GC system with multiple, distinct,
metallicity subpopulations, and this may argue against the "projection"
scenario, which posits that the ubiquitous color bimodality mainly results from
nonlinearities in the color-metallicity relations. Using optical, NIR, and
spectroscopic data, we found strong and consistent evidence of index
bimodality, which independently confirms the metallicity bimodality in NGC 3115
GCs. At the same time, we also found evidence for some color-color
nonlinearity. Taken in the broader context of previous studies, the multicolor
consistency of the GC bimodality in NGC 3115 suggests that in cases where GC
systems exhibit clear differences between their optical and optical-NIR color
distributions (as in some giant ellipticals), the apparent inconsistencies most
likely result from nonlinearities in the color-metallicity relations.
