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A large, complete, volume-limited sample of G-type dwarfs. I. Completion of Stroemgren UVBY photometry
Four-colour photometry of potential dwarf stars of types G0 to K2,selected from the Michigan Spectral Catalogues (Vol. 1-3), has beencarried out. The results are presented in a catalogue containing 4247uvby observations of 3900 stars, all south of δ = -26deg. Theoverall internal rms errors of one observation (transformed to thestandard system) of a program star in the interval 8.5 < V < 10.5are 0.0044, 0.0021, 0.0039, and 0.0059, respectively, in V, b-y, m_1_ ,and c_1_. The purpose of the catalogue, combined with earliercatalogues, is to allow selection of a large, complete, volume-limitedsample of G- and K-type dwarfs, investigate their metallicitydistribution, and compare it to predictions of various models ofgalactic chemical evolution. Future papers in this series will discussthese subjects.
| Evidence for an abundance gradient in the galactic disk
DDO photometry of field K giants in distant parts of the galactic diskin the galactic center and anticenter directions is used together withDDO and UBV photometry of 41 open clusters to investigate the variationof metallicity across the galactic disk. Some problems in thecalibration of DDO photometry are examined, and the observations areanalyzed. The data are shown to be consistent with the suggestion thatthere is a composition gradient among stars of all ages in the galacticdisk. Specifically, it is found that: (1) the metallicity gradient inthe solar vicinity is approximately -0.05/kpc; (2) the gradient maybecome steeper beyond a galactocentric distance of approximately 11 kpc;(3) the nitrogen gradient is more pronounced than the overall gradient;and (4) the gradient in the youngest stellar population is probably notdramatically different from the overall gradient
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