Astronomy and Astrophysics – Astrophysics
Scientific paper
2005-07-06
Astron.Lett. 31 (2005) 515-527
Astronomy and Astrophysics
Astrophysics
Accepted for 2005, Astronomy Letters, Vol. 31, No. 8, P.515-527; 14 pages, 6 figures
Scientific paper
The space velocities and Galactic orbital elements of stars calculated from the currently available high-accuracy observations in our summary catalog of spectroscopic magnesium abundances in dwarfs and subgiants in the solar neighborhood are used to identify thick-disk objects. The relative magnesium abundances in thick-disk stars are shown to lie within the range 0.0<[Mg/Fe]<0.5 and to decrease with increasing metallicity starting from [Fe/H]=-1.0. This is interpreted as evidence for a longer duration of the star formation process in the thick disk. We have found vertical gradients in metallicity (grad_Z[Fe/H]=-0.13\pm 0.04 kpc^{-1}) and relative magnesium abundance (grad_Z [Mg/Fe]=0.06\pm 0.02 kpc^{-1}), which can be present in the subsystem only in the case of its formation in a slowly collapsing protogalaxy. The large spread in relative magnesium abundance (-0.3<[Mg/Fe]<0.5) in the stars of the metal-poor "tail" of the thick disk which constitute 8% of the subsystem, can be explained in terms of their formation inside isolated interstellar clouds that interacted weakly with the matter of a single protogalactic cloud. We have found a statistically significant negative radial gradient in relative magnesium abundance in the thick disk (grad_R [Mg/Fe]=-0.03\pm 0.01 kpc^{-1}) instead of the expected positive gradient. The smaller perigalactic orbital radii and the higher eccentricities for magnesium-richer stars, which among other stars, are currently located in a small volume of the Galactic space near the Sun are assumed to be responsible for the gradient inversion. A similar but statistically less significant inversion is also observed in the subsystem for the radial metallicity gradient.
Borkova T. V.
Marsakov V. A.
No associations
LandOfFree
Formation of Galactic Systems in Light of the Magnesium Abundance in Field Stars: The Thick Disk does not yet have a rating. At this time, there are no reviews or comments for this scientific paper.
If you have personal experience with Formation of Galactic Systems in Light of the Magnesium Abundance in Field Stars: The Thick Disk, we encourage you to share that experience with our LandOfFree.com community. Your opinion is very important and Formation of Galactic Systems in Light of the Magnesium Abundance in Field Stars: The Thick Disk will most certainly appreciate the feedback.
Profile ID: LFWR-SCP-O-611061