Far-ultraviolet photometry of globular clusters with ANS - III. Globular cluster ages
Open Access
- 1 October 1981
- journal article
- research article
- Published by Oxford University Press (OUP) in Monthly Notices of the Royal Astronomical Society
- Vol. 196 (4) , 823-833
- https://doi.org/10.1093/mnras/196.4.823
Abstract
Synthesis of the far-ultraviolet colours of globular clusters in the ANS system has been carried out using isochrones and luminosity functions by Ciardullo & Demarque and theoretical ANS colours for the Kurucz-model atmospheres. For a sample of eight clusters with well-observed HR diagrams, we have subtracted the total horizontal branch flux from the ultraviolet colours and fitted the residual C18–25 colours to those of isochrones of various ages to yield ages of 11–14 × 109 yr. For a sample of seven low-metallicity clusters (group B) the observed scatter in the two-colour, C18–25, C15–33 diagram leads to an upper limit for the dispersion of the distribution of ages of 3 × 108 yr. From this we conclude that the volume containing the low-metallicity clusters has collapsed on a dynamical time-scale.Keywords
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