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S. S. Larsen, J. P. Brodie (UCO / Lick Observatory), D. A. Forbes, M. A. Beasley (Swinburne University)
We have obtained high signal-to-noise spectra for 13 globular clusters (GCs) in the Sombrero galaxy (NGC 4594). Using the new blue arm on the LRIS spectrograph on the Keck I telescope, we cover the wavelength region from 3700 Å to 8000 Å. From our spectroscopy we find that the globular clusters span a metallicity range from [Fe/H] = -0.1 to [Fe/H] = -1.9, similar to that of GCs in the Milky Way. Comparison of Balmer line indices with population synthesis models reveals no large age differences between metal-poor and metal-rich clusters. Using WFPC2 data from the HST archive, we have obtained V,I photometry for a larger sample of about 200 globulars in the Sombrero. Metallicities inferred from the V-I colors agree well with the spectroscopic ones and show a clearly bimodal distribution with mean metallicities of [Fe/H] = -1.4 and [Fe/H] = -0.5. Again, this is similar to the two peaks in the GC metallicity distributions in the Milky Way and M31, as well as many large ellipticals. Due to the large number of metal-rich GCs in the Sombrero, we associate them with the bulge rather than the disk. The HST data also reveal a correlation between GC sizes and metallicities similar to that seen in many ellipticals and the Milky Way.