J/AJ/109/1095 Thick Disk Chemical Abundance Distribution (Gilmore+ 1995)
A determination of the thick disk chemical abundance distribution:
implications for galaxy evolution.
Gilmore G., Wyse R.F.G., Jones J.B.
<Astron. J. 109, 1095 (1995)>
=1995AJ....109.1095G 1995AJ....109.1095G
ADC_Keywords: Photometry, photographic ; Stars, distances ;
Effective temperatures
Description:
We present a determination of the thick disk iron abundance
distribution obtained from an in situ sample of F/G stars. These stars
are faint, 15≤V=<18, selected on the basis of color, being a subset
of the larger survey of Gilmore and Wyse designed to determine the
properties of the stellar populations several kiloparsecs from the
Sun. The fields studied in the present paper probe the iron abundance
distribution of the stellar populations of the galaxy at 500-3000pc
above the plane, at the solar Galactocentric distance. The derived
chemical abundance distributions are consistent with no metallicity
gradients in the thick disk over this range of vertical distance, and
with an iron abundance distribution for the thick disk that has a peak
at -0.7dex. The lack of a vertical gradient argues against slow,
dissipational settling as a mechanism for the formation of the thick
disk. The photometric and metallicity data support a turn-off of the
thick disk that is comparable in age to the metal-rich globular
clusters, or ≥12Gyr, and are consistent with a spread to older ages.
File Summary:
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FileName Lrecl Records Explanations
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ReadMe 80 . This file
table2.dat 55 133 Observed and derived data for South Galactic
Pole stars
table4.dat 55 87 Observed and derived data for UK Schmidt
Field 117 stars (l, b)=(270, -45)
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Byte-by-byte Description of file: table2.dat table4.dat
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Bytes Format Units Label Explanations
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1 I1 h RAh Right ascension 1950.0
3- 4 I2 min RAm Right ascension 1950.0
6- 10 F5.2 s RAs Right ascension 1950.0
12 A1 --- DE- Declination sign
13- 14 I2 deg DEd Declination 1950.0
16- 17 I2 arcmin DEm Declination 1950.0
19- 22 F4.1 arcsec DEs Declination 1950.0
24- 28 F5.2 mag Vmag V magnitude
30- 33 F4.2 mag B-V B-V color index
35- 38 F4.2 mag V-I V-I color index
40- 44 F5.2 Sun [Fe/H] Metallicity
46- 49 I4 pc Dist Distance from photometric parallax
51- 54 I4 K Teff Effective temperature from V-I
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Courtesy: Rosie Wyse
(End) Patricia Bauer [CDS] 14-Jun-1996