Age of Globular Clusters

QING ZHANG
Department of Physics and Astronomy
The Johns Hopkins University

Abstract

This paper reports the re-estimated distances and ages of Galactic globular clusters (GCs) using the newly released Hipparcos high precision trigonometric parallaxes data. By adopting carefully selected subdwarfs with low metallicity as well as appropriate brightness, the distances of the globular clusters are estimated to be larger and hence their ages are younger than previously accepted values. Different techniques taken by several groups in measuring GC distances are compared. A typical value estimated for the oldest GCs is Gyr. This younger age of oldest GCs eliminates its discrepancy with that from standard inflationary models for the universe.

Keywords: clusters: globular -cosmology: theory - distance scale

 
• Introduction
• Techniques of distance determination
  • Reid's subdwarf fitting
  • Gratton et al.'s distance determination
  • Chaboyer et al.'s subdwarf main sequence fitting
• M(HB), Distance to LMC and Ages of GCs
• Discussion
• Appendix
• References
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