Globular Clusters, Dark Matter Halos, Galaxy Formation, and the Age of the Universe

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Session 69 -- Invited Talks
Invited presentation, Thursday, January 13, 4:00-5:30, Salons III/IV Room (Crystal Gateway)

[69.02] Globular Clusters, Dark Matter Halos, Galaxy Formation, and the Age of the Universe

M. Bolte (UCO/Lick Observatory)

The state-of-the-observations in three areas where globular cluster research impacts other fields of astronomy are presented. \par 1) Very deep luminosity functions for GGC have shown an upturn at faint magnitudes and if, by analogy, the same is true for the field Pop II LF of the halo, it has been suggested that low-mass Pop II field stars can account for the inferred dark halo of the Galaxy (e.g. Richer et al., ApJ, 381, 147). The difficulties in making such measurements and in interpreting the observations will be discussed. \par 2) The precision with which relative cluster ages can be measured has improved to the point where detection and non-detection of ages differences between clusters can put meaningful constraints on scenarios of the formation of the halo. The important results to date are that there are unambiguosly determined age differences between some clusters, but the majority of GGC may be coeval at the level of 1 Gyr (Bolte, ASP Conf. Ser. 48, p. 60). Although there is little hard information about trends in age with Galactocentric radius, the cluster age distribution is most consistent with a largely uniform age for the halo in which the majority of the star formation occured in a fast collapse phase with a small fraction of late cluster formation or perhaps the accretion of a companion. \par 3) GGC absolute ages can provide one of the strongest constraints on world models by setting a lower limit to the age of the Universe. Although the formal errors in determining cluster ages remain of order 3 Gyr, the most reliably measured GGC ages are $>15$ Gyr and can be used to rule out $\Omega=1$, $H_0>80$, $\Lambda=0$ solutions to the equations of general relavity.

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