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The Universe and Globular Clusters: An Age Conflict?

1997; IOP Publishing; Volume: 477; Issue: 2 Linguagem: Inglês

10.1086/303724

1538-4357

F. D’Antona, V. Caloi, I. Mazzitelli,

Gamma-ray bursts and supernovae

Chaboyer (1995) has recently shown that the range of possible ages of globular clusters, τ ~ 14-18 Gyr, corresponding to different choices of distance scales, is further enlarged mainly by uncertainties in modeling convection. Within the mixing-length theory (MLT) the result is τ = 11-21 Gyr. Bolte & Hogan (1995) adopted the field subdwarfs as indicators of the distance scale and, assuming that τ is insensitive to the treatment of convection, found that τ = (15.8 ± 2.1) Gyr. Within Chaboyer's findings, it is marginally possible to avoid an "age conflict" with the expansion age of the universe, even if this latter is t0 = 8-11 Gyr, while this is not the case with the Bolte & Hogan (1995) conclusion. Mazzitelli, D'Antona, & Caloi (1995) have implemented updated macro- and microphysics inputs and determined the distance scale by fitting the horizontal-branch models to the horizontal branch of metal-poor globular clusters. Within the MLT, they find τ ≃ 14 Gyr. Switching from MLT to a full spectrum of turbulence (FST) model of convection (Canuto & Mazzitelli 1991) lowers the value of τ by 1-2 Gyr. Since the Mazzitelli et al. (1995) results would alleviate the age conflict to the point of making it disappear, it is important to assess their validity by answering the following questions. Independently of the assumptions on the distance scale: