ARlogo Annu. Rev. Astron. Astrophys. 1996. 34: 461-510
Copyright © 1996 by Annual Reviews. All rights reserved

Reprinted with kind permission from Annual Reviews, 4139 El Camino Way, Palo Alto, California, USA

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THE AGE OF THE GALACTIC GLOBULAR CLUSTER SYSTEM

Don A. VandenBerg 1

Department of Physics and Astronomy, University of Victoria, P. O. Box 3055, Victoria, British Columbia, Canada V8W 3P6

Michael Bolte

UCO/Lick Observatory, University of California, Santa Cruz, California 95064

Peter B. Stetson

Dominion Astrophysical Observatory, Herzberg Institute of Astrophysics, National Research Council of Canada, 5071 West Saanich Road, Victoria, British Columbia, V8X 4M6 Canada


ABSTRACT. A careful assessment of current uncertainties in stellar physics (opacities, nuclear reaction rates, equation of state effects, diffusion, rotation, and mass loss), in the chemistry of globular cluster (GC) stars, and in the cluster distance scale, suggests that the most metal-poor (presumably the oldest) of the Galaxy's GCs have ages near 15 Gyr. Ages below 12 Gyr or above 20 Gyr appear to be highly unlikely. If these approx 2sigma limits are increased by ~ 1 Gyr to account for the formation time of the globulars, and if standard Friedmann cosmologies with the cosmological constant set to zero are assumed, then the GC constraint on the present age of the Universe (t0 geq 13 Gyr) implies that the Hubble constant H0 leq 51 km s-1 Mpc-1 if the density parameter Omega = 1 or leq 62 km s-1 Mpc-1 if Omega = 0.3.


Key words: globular clusters, stellar structure, stellar evolution, ages, subdwarfs, RR Lyrae stars, chemical abundances, cosmology


Table of Contents

INTRODUCTION

THE STELLAR EVOLUTION CLOCK
Uncertainty in LTO Due to Basic Stellar Physics Inputs
Uncertainty in LTO Due to Additional Physics Usually ignored
Uncertainty in LTO Due to Unconventional Physics
Uncertainty in LTO Due to the Assumed Chemistry of Stars
Tests of Stellar Models
The First Estimates of Globular Cluster Ages

GLOBULAR CLUSTER DISTANCES
Subdwarf-Based Distances
Distances Based on RR Lyraes

SUMMARY

REFERENCES



1 Killam Research Fellow. Back.

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