Ages and metallicities of globular clusters in NGC 4472

Beasley, M. A.; Sharples, R. M.; Bridges, T. J.; Hanes, D. A.; Zepf, S. E.; Ashman, K. M.; Geisler, D.
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Monthly Notices of the Royal Astronomical Society, Volume 318, Issue 4, pp. 1249-1263.

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We have derived ages and metallicities from co-added spectra of 131 globular clusters associated with the giant elliptical galaxy NGC 4472. Based upon a calibration with Galactic globular clusters, we find that our sample of globular clusters in NGC 4472 span a metallicity range of approximately -1.6<=[Fe/H]<=0dex. There is evidence of a radial metallicity gradient in the globular cluster system which is steeper than that seen in the underlying starlight. Determination of the absolute ages of the globular clusters is uncertain, but formally, the metal-poor population of globular clusters has an age of 14.5+/-4Gyr and the metal-rich population is 13.8+/-6Gyr old. Monte Carlo simulations indicate that the globular cluster populations present in these data are older than 6Gyr at the 95per cent confidence level. We find that within the uncertainties, the globular clusters are old and coeval, implying that the bimodality seen in the broadband colours primarily reflects metallicity and not age differences.