Hubble Space Telescope photometry of globular clusters in the Sombrero galaxy |
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Authors: | Søren S Larsen Duncan A Forbes Jean P Brodie |
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Institution: | 1UC Observatories/Lick Observatory, University of California Santa Cruz, CA 95064, USA;2Astrophysics &Supercomputing, Swinburne University, Hawthorn VIC 3122, Australia |
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Abstract: | We explore the rich globular cluster (GC) system of the nearby Sa galaxy M104, the 'Sombrero' (NGC 4594), using archive Wide Field Planetary Camera 2 data. The GC colour distribution is found to be bimodal at the >99 per cent confidence level, with peaks at and . The inferred metallicities are very similar to those of GCs in our Galaxy and M31. However, the Sombrero reveals a much enhanced number of red (metal-rich) GCs compared to other well-studied spirals. Because the Sombrero is dominated by a huge bulge and only has a modest disc, we associate the two subpopulations with the halo and bulge components, respectively. Thus our analysis supports the view that the metal-rich GCs in spirals are associated with the bulge rather than with the disc. The Sombrero GCs have typical effective (half-light) radii of ~2 pc with the red ones being ~30 per cent smaller than the blue ones. We identify many similarities between the GC system of the Sombrero and those of both late-type spirals and early-type galaxies. Thus both the GC system and the Hubble type of the Sombrero galaxy appear to be intermediate in their nature. |
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Keywords: | galaxies: individual: M104 (NGC 4594) galaxies: spiral galaxies: star clusters |
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