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Session 83 - Elliptical Galaxies.
Display session, Wednesday, January 17
North Banquet Hall, Convention Center
The globular cluster system of the giant elliptical galaxy NGC 4472 in the Virgo cluster is investigated. We have obtained deep images in the C and T_1 filters of the Washington system using the KPNO 4m PF/CCD. The photometry reaches to T_1 \sim R\sim 25, well beyond the turnover in the cluster luminosity function. The color-magnitude diagram and image classification are used to select out a highly-probable set of about 1800 globular clusters (\sim 1/4 of the total in this galaxy) which are then subjected to abundance analysis. The internal metallicity errors are less than 0.15 dex. This is by far the largest dataset of this kind yet available. The median metal abundance of the NGC 4472 globular clusters is [Fe/H]=-0.9. The metallicity distribution is clearly bimodal, with peaks at [Fe/H]\sim -1.2 and -0.1. The clusters in the metal-rich peak are found to be much more concentrated to the center of NGC 4472 than the metal-poor clusters. This evidence is in very strong support of the idea of globular cluster formation in mergers put forth by Ashman and Zepf. It appears that NGC 4472 has 2 distinct cluster populations. We also investigate the luminosity function of the globulars and its use as a distance indicator.
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