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II/180 uvby-beta photometry of metal-poor stars (Schuster+ 1989)
The following files can be converted to FITS (extension .fit .fit.Z .fgz)
table1
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Query from: http://vizier.cds.unistra.fr/viz-bin/VizieR?-source=II/180
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-r--r--r-- 1 cats archive 12958 Jan 4 1993 table1 Beginning of ReadMe :II/180 uvby-beta photometry of metal-poor stars (Schuster+ 1989)
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uvby-beta photometry of high-Velocity and metal-poor stars
Schuster W.J., Nissen P.E.
<Astron. Astrophys. 222, 69 (1989)>
=1989A&A...222...69S
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ADC_Keywords: Stars, high-velocity ; Stars, metal-deficient
Keywords: evolution of the Galaxy - halo stars - metallicity - ages
Description:
Using the calibrations derived by Schuster and Nissen
(=1989A&A...221...65S), the interstellar color excesses, E(b-y), and
the metallicities, [Fe/H], have been determined for the 711 high
velocity and metal-poor stars in the catalogue of uvby-beta photometry
(=1988A&AS...73..225S). 220 of these listed in table1 turn out to be
halo stars according to the criterion [Fe/H] <= -1.0. About 15% of
the halo stars have colors that are significantly affected by
interstellar reddening, i.e. E(b-y) > 0.025.
The distributions in the c0-(b-y)0 diagram of the halo stars grouped
according to [Fe/H], have well defined turn-off points. From the Teff
values of these points a minimum age of 18-20 Gyr for the halo stars
is determined. However, this age may be 2-3 Gyr too high due to a
possible systematic error in Teff for the stellar models used.
Relative ages of 77 halo stars in the turn-off region of the c0-(b-y)0
diagram are derived using the isochrones VandenBerg and Bell
(=1985ApJS...58..561V). Assuming that the O/Fe abundance ratio is
constant in halo stars, evidence of a cosmic age scatter of
+/-2.5Gyr at a given metallicity is found. Furthermore, the mean age
of the halo stars is found to decrease smoothly by about 3 Gyr from
[Fe/H]= -2.0 to -1.0. These results suggest that a pressure-supported
slow uniform collapse controlled the formation and early evolution of
the Galaxy. However, the scenario of Searle and Zinn
(=1978ApJ...225..357S) is also compatible with the results.