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Your search keyword '"Ruchti G.R."' showing total 2 results
Start Over Author "Ruchti G.R." Publisher edp sciences
2 results on '"Ruchti G.R."'

1. Origins of the thick disk of the galaxy as traced by metal-poor stars selected from RAVE

Author

Ruchti G.R.

Subjects
Physics, QC1-999
Abstract

Models of the formation of the thick disk of the Milky Way Galaxy make specific predictions about the chemical abundance properties of the metal-weak (and oldest) stellar population in the thick disk. We have undertaken the study of the elemental abundances and kinematic properties of a sample of 319 candidate metal-poor thick-disk stars selected from the RAVE spectroscopic survey of bright stars. Our aim is to differentiate among the present scenarios of the formation of the thick disk. In this study, we measured the abundances of several alpha-elements and found that the thick-disk [alpha/Fe] ratios are enhanced, implying that enrichment proceeded by purely core-collapse supernovae. Further, the sample probes distances ranging out to about 2 kpc from the Sun, allowing for the investigation of the gradients in the thick disk. I will discuss the results from these investigations and how they compare to the predictions made by present models of the formation of the thick disk.

Published
2012
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2. TheGaia-ESO Survey: radial metallicity gradients and age-metallicity relation of stars in the Milky Way disk

Author

M. Bergemann, G. R. Ruchti, A. Serenelli, S. Feltzing, A. Alves-Brito, M. Asplund, T. Bensby, P. Gruiters, U. Heiter, A. Hourihane, A. Korn, K. Lind, A. Marino, P. Jofre, T. Nordlander, N. Ryde, C. C. Worley, G. Gilmore, S. Randich, A. M. N. Ferguson, R. D. Jeffries, G. Micela, I. Negueruela, T. Prusti, H.-W. Rix, A. Vallenari, E. J. Alfaro, C. Allende Prieto, A. Bragaglia, S. E. Koposov, A. C. Lanzafame, E. Pancino, A. Recio-Blanco, R. Smiljanic, N. Walton, M. T. Costado, E. Franciosini, V. Hill, C. Lardo, P. de Laverny, L. Magrini, E. Maiorca, T. Masseron, L. Morbidelli, G. Sacco, G. Kordopatis, G. Tautvaišienė, Universidad de Alicante. Departamento de Física, Ingeniería de Sistemas y Teoría de la Señal, Astrofísica Estelar (AE), Bergemann M., Ruchti G.R., Serenelli A., Feltzing S., Alves-Brito A., Asplund M., Bensby T., Gruiters P., Heiter U., Hourihane A., Korn A., Lind K., Marino A., Jofre P., Nordlander T., Ryde N., Worley C.C., Gilmore G., Randich S., Ferguson A.M.N., Jeffries R.D., Micela G., Negueruela I., Prusti T., Rix H.-W., Vallenari A., Alfaro E.J., Allende Prieto C., Bragaglia A., Koposov S.E., Lanzafame A.C., Pancino E., Recio-Blanco A., Smiljanic R., Walton N., Costado M.T., Franciosini E., Hill V., Lardo C., De Laverny P., Magrini L., Maiorca E., Masseron T., Morbidelli L., Sacco G., Kordopatis G., and Tautvaisiene G.

Subjects
Solar neighborhood, Milky Way, Metallicity, Formation, FOS: Physical sciences, Galaxia, Astrophysics::Cosmology and Extragalactic Astrophysics, Astrophysics, Surveys, fundamental parameters [Stars], Astronomia ultravioleta, 01 natural sciences, Spectral line, Galaxy: disk, Stars:fundamental parameter, Fundamental parameters, 0103 physical sciences, Astrophysics::Solar and Stellar Astrophysics, Abundances, Disc, 010303 astronomy & astrophysics, Astrophysics::Galaxy Astrophysics, Astronomía y Astrofísica, Mapeamentos astronômicos, Physics, 010308 nuclear & particles physics, Plane (geometry), Stars:abundance, Vertical distance, Astronomy and Astrophysics, Composicao estelar, Astrophysics - Astrophysics of Galaxies, Espectros estelares, Stars, Galaxy, formation [Galaxy], Galaxy: formation, Disk, Space and Planetary Science, abundances [Stars], Astrophysics of Galaxies (astro-ph.GA), Magnitude (astronomy), Astrophysics::Earth and Planetary Astrophysics, disk [Galaxy]
Abstract

We study the relationship between age, metallicity, and alpha-enhancement of FGK stars in the Galactic disk. The results are based upon the analysis of high-resolution UVES spectra from the Gaia-ESO large stellar survey. We explore the limitations of the observed dataset, i.e. the accuracy of stellar parameters and the selection effects that are caused by the photometric target preselection. We find that the colour and magnitude cuts in the survey suppress old metal-rich stars and young metal-poor stars. This suppression may be as high as 97% in some regions of the age-metallicity relationship. The dataset consists of 144 stars with a wide range of ages from 0.5 Gyr to 13.5 Gyr, Galactocentric distances from 6 kpc to 9.5 kpc, and vertical distances from the plane 0 < |Z| < 1.5 kpc. On this basis, we find that i) the observed age-metallicity relation is nearly flat in the range of ages between 0 Gyr and 8 Gyr; ii) at ages older than 9 Gyr, we see a decrease in [Fe/H] and a clear absence of metal-rich stars; this cannot be explained by the survey selection functions; iii) there is a significant scatter of [Fe/H] at any age; and iv) [Mg/Fe] increases with age, but the dispersion of [Mg/Fe] at ages > 9 Gyr is not as small as advocated by some other studies. In agreement with earlier work, we find that radial abundance gradients change as a function of vertical distance from the plane. The [Mg/Fe] gradient steepens and becomes negative. In addition, we show that the inner disk is not only more alpha-rich compared to the outer disk, but also older, as traced independently by the ages and Mg abundances of stars., accepted for publication in A&A

Published
2014
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