Abundances in G. Dwarfs.VI. a Survey of Field Stars.

Data are presented for deriving the abundances of the elements in 21 field stars of very nearly solar type. Iron-to-hydrogen ratios are obtained from curves of growth for which the ionization temperatures are determined by considering both the excitation temperatures and the effective temperatures. The effective temperatures are derived both from the B - V colors (corrected for line blanketing) and the G - R colors of the sincolor photometry system. The abundance ratios of ten other elements to iron are then derived. This material is combined with results for 13 other G dwarfs already published and is discussed from the point of view both of the nuclear reactions responsible for element building and of problems of galactic structure and stellar populations. The following points are discussed: 1. There seems to be a correlation between a star's metal abundances and the velocity parameter derived from the curve of growth, in that stars with low metal content have less turbulence. 2. The correlation between a G dwarf's ultraviolet excess and its metal deficiency is confirmed and strengthened. 3. The relative abundances of the metals do not remain constant, in particular: (a) all metal-poor stars and a few normal stars show a deficiency of manganese with respect to the other iron peak elements, chromium, nickel, and iron; (b) seven stars show an excess of Mg, Si, Ca, and Ti with respect to the iron peak elements as well as the other light elements, Na and Sc. These four elements are all formed by the addition of successive a-particles to Ne'0. 4. Trigonometric parallaxes show that 7 stars definitely lie above the main sequence. Six of these must be very old, about 15 X 10 years, and 4 of these 6 are slightly metal-rich. 5. A discussion of the motions of these stars in the galactic plane shows that both metal-rich and metal-poor stars are found with nearly circular orbits, but all the stars with large velocities with respect to the local standard of rest are metal-poor. 6. When the stars are plotted in the Haas-Bottlinger diagram with the ratio of the a-elements (Mg, Si. Ca, and Ti) to iron as the parameter, a clear division is seen, in that all the a-rich stars are high-velocity stars whose perigalactic distances are about -,` or less than the distance from the sun to the galactic center. All metal-poor stars with velocities near the circular velocity have normal ratios of the a-elements to iron. Such a separation is taken to indicate that the high-velocity stars were formed in their present orbits rather than having been scattered out of circular orbits. 7. An analysis of the motions perpendicular to the galactic plane shows that the velocity dispersion increases steadily for stars of increasing metal deficiency.