Spectra of globular clusters in the Sombrero galaxy: evidence for
  spectroscopic metallicity bimodality
  We present a large sample of over 200 integrated-light spectra of confirmed
globular clusters (GCs) associated with the Sombrero (M104) galaxy taken with
the DEIMOS instrument on the Keck telescope. A significant fraction of the
spectra have signal-to-noise levels high enough to allow measurements of GC
metallicities using the method of Brodie & Huchra (1990). We find a
distribution of spectroscopic metallicities ranging from -2.2 < [Fe/H] < +0.1
that is bimodal, with peaks at [Fe/H] ~ -1.4 and -0.6. Thus the GC system of
the Sombrero galaxy, like a few other galaxies now studied in detail, reveals a
bimodal spectroscopic metallicity distribution supporting the long-held belief
that colour bimodality reflects two metallicity subpopulations. This further
suggests that the transformation from optical colour to metallicity for old
stellar populations, such as GCs, is not strongly non-linear. We also explore
the radial and magnitude distribution with metallicity for GC subpopulations
but small number statistics prevent any clear trends in these distributions.
