相关论文: The origin of nitrogen: Implications of recent mea…
We have composed a sample of 68 massive stars in our galaxy whose projected rotational velocity, effective temperature and gravity are available from high-precision spectroscopic measurements. The additional seven observed variables…
We determine magnesium isotopic abundances of metal poor dwarf stars from the galactic halo, to shed light on the onset of asymptotic giant branch (AGB) star nucleossynthesis in the galactic halo and constrain the timescale of its…
The orbital motions of halo stars in the Milky Way reflect the orbital motions of the progenitor systems in which they formed, making it possible to trace the mass-assembly history of the Galaxy. Direct measurement of three-dimensional…
We have investigated the oxygen and nitrogen chemical abundances in extremely compact star-forming galaxies with redshifts between $\sim$0.11-0.35, popularly referred to as "green peas". Direct and strong-line methods sensitive to the N/O…
We introduce a stochastic halo formation model to compute the early chemical enrichment of the interstellar medium (ISM) of the halo. Contrary to 1-zone chemical evolution models, we are able to resolve local inhomogeneities in the ISM…
The current knowledge of the abundance structure in the Milky Way is reviewed. Special emphasis is put on recent results for stars with kinematics typical of the thin and the thick disks, respectively, and how these results can, apart from…
In this work we present the main atmospheric parameters, carbon, nitrogen and oxygen abundances, and 12C/13C ratios determined in a sample of 28 Galactic clump stars. Abundances of carbon were studied using the C2 band at 5086.2 {\AA}. The…
We present a method to determine nitrogen abundance ratios with respect to iron ([N/Fe]) from molecular CN-band features observed in low-resolution ($R \sim$ 2000) stellar spectra obtained by the Sloan Digital Sky Survey (SDSS) and the…
We examine how the cosmic environment affects the chemical evolution of galaxies in the Universe by comparing the N/O ratio of dwarf galaxies in voids with dwarf galaxies in more dense regions. Ratios of the forbidden [O III] and [S II]…
Chemical evolution models for the Galactic disk under an inside-out formation scenario are presented for seven sets of stellar yields, all of them metal dependent. In particular, the effects of yields from massive and…
One way to constrain the nature of the high-redshift progenitors of the Milky Way is to look at the low-metallicity stellar populations of the different Galactic components today. For example, high-resolution spectroscopy of very metal poor…
The earliest phases of the chemical evolution of our Galaxy are analysed in the light of the recent VLT results (concerning abundance patterns in the most metal-poor stars of the Galactic halo) and of stellar nucleosynthesis calculations.…
Theoretically, rotation-induced chemical mixing in massive stars has far reaching evolutionary consequences, affecting the sequence of morphological phases, lifetimes, nucleosynthesis, and supernova characteristics. Using a sample of 72…
We study the redshift evolution of the gas-phase O/H and N/O abundances, both (i) for individual ISM regions within single spatially-resolved galaxies and (ii) when dealing with average abundances in the whole ISM of many unresolved…
For the first time, a direct NLTE analysis of carbon and nitrogen lines in the spectra of nine RR Lyrae stars was carried out. We have determined the abundances of these elements together with oxygen, and have shown that the nitrogen…
Observations of low-metallicity halo stars have revealed a puzzling result: the abundance of \li7 in these stars is at least three times lower than their predicted primordial abundance. It is unclear whether the cause of this disagreement…
With abundances and 2{\sigma} upper limits of fluorine (F) in seven metal-poor field giants, nucleosynthesis of stellar F at low metallicity is discussed. The measurements are derived from the HF(1-0) R9 line at 23358{\AA} using…
Evolutionary models for massive stars, accounting for rotational mixing effects, do not predict any core-processed material at the surface of B dwarfs with low rotational velocities. Contrary to theoretical expectations, we present a…
The oldest, most metal-poor stars in the Galactic halo and satellite dwarf galaxies present an opportunity to explore the chemical and physical conditions of the earliest star forming environments in the Universe. We review the fields of…
The first stars are predicted to have formed within 200 million years after the Big Bang, initiating the cosmic dawn. A true first star has not yet been discovered, although stars with tiny amounts of elements heavier than helium ('metals')…