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Abundances for alpha-elements and Fe in about 150 field subdwarfs and early subgiants with accurate parallaxes and kinematic data are used to discuss the run of abundance ratios in metal-poor stars in the solar neighborhood. Based on…

The supernova yields of several heavy elements including alpha-, iron-group, and r-process elements are obtained as a function of the mass of their progenitor main-sequence stars M_ms from the abundance patterns of extremely metal-poor…

Astrophysics · Physics 2009-10-31 Takuji Tsujimoto , Toshikazu Shigeyama

Understanding the history and the evolution of the Milky Way disc is one of the main goals of modern astrophysics. We study the velocity dispersion behaviour of Galactic disc stars as a function of the [Mg/Fe] ratio, which can be used as a…

Linear [Q/H]-[O/H] relations, Q = Na, Mg, Si, Ca, Ti, Cr, Fe, Ni, are inferred from a sample (N=67) of recently studied FGK-type dwarf stars in the solar neighbourhood including different populations. Regression line slope and intercept…

Astrophysics of Galaxies · Physics 2013-12-24 R. Caimmi

We have determined beryllium abundances for 25 metal-poor stars based on the high resolution and high signal-to-noise ratio spectra from the VLT/UVES database. Our results confirm that Be abundances increase with Fe, supporting the global…

Astrophysics · Physics 2009-11-13 K. F. Tan , J. R. Shi , G. Zhao

From a detailed elemental abundance analysis of 102 F and G dwarf stars we present abundance trends in the Galactic thin and thick disks for 14 elements (O, Na, Mg, Al, Si, Ca, Ti, Cr, Fe, Ni, Zn, Y, Ba, and Eu). Stellar parameters and…

Astrophysics · Physics 2007-05-23 T. Bensby , S. Feltzing , I. Lundström , I. Ilyin

The spatial distribution of elemental abundances and their time evolution are among the major constraints to disentangle the scenarios of formation and evolution of the Galaxy. We used the sample of open clusters available in the final…

CNO abundances in galaxies bear on issues of galactic evolution as well as stellar evolution and nucleosynthesis. Knowledge about them in dwarf and spiral galaxies depends mainly on emission lines from H II regions, with information from…

Astrophysics · Physics 2007-05-23 B. E. J. Pagel

We discuss the evolution of oxygen, carbon and nitrogen in galaxies of different morphological type by adopting detailed chemical evolution models with different star formation histories (continuous star formation or starbursts). We start…

Astrophysics · Physics 2009-11-07 Cristina Chiappini , Donatella Romano , Francesca Matteucci

Fully cosmological, high resolution N-Body + SPH simulations are used to investigate the chemical abundance trends of stars in simulated stellar halos as a function of their origin. These simulations employ a physically motivated supernova…

Astrophysics of Galaxies · Physics 2015-05-18 Adi Zolotov , Beth Willman , Alyson Brooks , Fabio Governato , David W. Hogg , Sijing Shen , James Wadsley

Recent observations of heavy elements produced by rapid neutron capture (r-process) in the halo have shown a striking and unexpected behavior: within a single star, the relative abundances of r-process elements heavier than Eu are the same…

Astrophysics · Physics 2009-11-06 Brian D. Fields , James W. Truran , John J. Cowan

The factors influencing chemical evolution of galaxies are poorly understood. Both gas inflow and gas outflow reduce a gas-phase abundance of heavy elements (metallicity) whereas the ongoing star formation continuously increases it. To…

Astrophysics of Galaxies · Physics 2015-12-16 A. Zasov , A. Saburova , O. Abramova

We present isochrone ages and initial bulk metallicities ($\rm [Fe/H]_{bulk}$, by accounting for diffusion) of 163,722 stars from the GALAH Data Release 2, mainly composed of main sequence turn-off stars and subgiants ($\rm 7000…

Lithium abundance in most of the warm metal-poor main sequence stars shows a constant plateau (A(Li)~2.2 dex) and then the upper envelope of the lithium vs. metallicity distribution increases as we approach solar metallicity. Meteorites,…

In some recent works, the C/O abundance ratio in high-metallicity stars with planets is found to vary from 0.4 to about 1.0. This has led to discussions about the existence of terrestrial planets with a carbon-dominated composition that is…

Solar and Stellar Astrophysics · Physics 2015-06-15 Poul Erik Nissen

We present a detailed and uniform study of oxygen abundance from two different oxygen lines at 6158$\AA$ and 6300$\AA$ in a large sample of solar-type stars. The results are used to check the behaviour of these spectral lines as oxygen…

Solar and Stellar Astrophysics · Physics 2015-04-15 S. Bertran de Lis , E. Delgado Mena , V. Zh. Adibekyan , N. C. Santos , S. G. Sousa

We investigate the oxygen and nitrogen abundance distributions across the optical disks of 130 nearby late-type galaxies using around 3740 published spectra of HII regions. We use these data in order to provide homogeneous abundance…

Astrophysics of Galaxies · Physics 2015-06-19 L. S. Pilyugin , E. K. Grebel , A. Y. Kniazev

Using data from the GALAH survey, we explore the dependence of elemental abundances on stellar age and metallicity among Galactic disc stars. We find that the abundance of most elements can be predicted from age and [Fe/H] with an intrinsic…

Recent work suggests that galaxy evolution, and the build-up of stellar mass (M*) over cosmic time, is characterized by changes with redshift of star formation rate (SFR) and oxygen abundance (O/H). In a companion paper, we have compiled a…

Astrophysics of Galaxies · Physics 2016-08-31 Leslie Hunt , Pratika Dayal , Laura Magrini , Andrea Ferrara

We develop a hybrid model of galactic chemical evolution that combines a multi-ring computation of chemical enrichment with a prescription for stellar migration and the vertical distribution of stellar populations informed by a cosmological…