Distances and Absolute Ages of Galactic Globular Clusters from Hipparcos Parallaxes of Local Subdwarfs
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چکیده
High precision trigonometric parallaxes from the Hipparcos satellite and accurate metal abundances ((Fe/H], O/Fe], and /Fe]) from high resolution spectroscopy for about 30 local subdwarfs have been used to derive distances and ages for a carefully selected sample of nine globular clusters. We nd that Hipparcos parallaxes are smaller than the corresponding ground-based measurements leading, to a longer distance scale (0:2 mag) and to ages 2:8 Gyr younger. The relation between the zero age horizontal branch (ZAHB) absolute magnitude and metallicity for the nine programme clusters is: The corresponding Large Magellanic Cloud distance modulus is (m ? M) 0 = 18:61 0:07. The age of the bona de old globular clusters (Oosterhoo II and Blue Horizontal Branch) based on the absolute magnitude of the turn-oo is: age = 11:8 +2:1 ?2:5 Gyr The present age of globular clusters no longer con-icts with standard innationary models for the Universe .
منابع مشابه
Distances and Absolute Ages of Galactic Globular Clusters from Hipparcos Parallaxes of Local Subdwarfs *
High precision trigonometric parallaxes from the HIPPARCOS satellite and accurate metal abundances ([Fe/H], [O/Fe], and [α/Fe]) from high resolution spectroscopy for about 30 local subdwarfs have been used to derive distances and ages for a carefully selected sample of nine globular clusters. We find that HIPPARCOS parallaxes are smaller than the corresponding ground-based measurements leading,...
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