Sobre a relação metalicidade-idade-distância para estrelas do tipo F e G na vizinhança solar

Abstract

The age-metallicity relation constitutes a fundamental observation to detail the chemical-time evolution of the galactic disk. However, this relation still has a controversial history in the literature. For this work, it is suggested the addition of the distance parameter, from the Sun to the star R and the XYZ Cartesian planes of the galactic disk in this relation with the aiming to trace its behavior. For this purpose, it was used a F and G spectral types single star’s sample in the solar neighborhood from the Geneva-Copenhagen survey (GCS) catalog, which holds [Fe/H] derived from the system uvby by Strömgren, distances resulting from parallax of the Hipparcos and Tycho-2 catalogs and computed ages of theoretical isochrones. The final sample, therefore, has 2215 single dwarf stars, aged less than 10 giga-years with an error of less than 25%, distances up to the Sun R 120 pc and, in the great majority, poor in metals. Based on the results, it can be seen that the dispersion in the age-metallicity relation already detected in the current literature, extends across the entire age range for type G stars, however, for those of type F, the relation showed an explicit gradual decline. In addition, the dispersion behavior in this relation tends to be greater for metal-poor G stars than for type F stars. We found the presence of stars with [Fe/H] < 0 both near and far to the Sun, with manifestations of stars with [Fe/H] < -0.4 in regions between 80 < R < 120 for type F and between 70 < R < 90 for type G. In addition, those of type G emphasize the assiduity from young stars to greater distances. We also used the resampling method bootstrap to ascertain the behavior of the dispersion of [Fe/H] on the physical planes. It has been found that the edges of these planes are the most likely regions of heating effects, where it may be associated with contamination by mass or other stellar properties. The age-metallicity-distance analysis intensified the concept of orbital diffusion in the solar neighborhood, a factor that may be one of the mechanism responsible for the appearance of a decrease in metallicity in the same age range of stars close to greater distances.