Related papers: Evolution and chemical and dynamical effects of hi…
Recent studies show that the chemical evolution of Sr and Ba in the Galaxy can be explained if different production sites, hosting r- and s-processes, are taken into account. However, the question of unambiguously identifying these sites is…
High redshift DLA systems suggest that the relative abundances of elements might be roughly solar, although with absolute abundances of more than two orders of magnitude below solar. The result comes from observations of the [SII/ZnII]…
Our knowledge of galactic chemical evolution is currently limited to observations of Milky Way stars and H II regions of nearby galaxies. Damped Lyman~$\alpha$ systems offer a new approach for tracking the evolution of normal galaxies from…
A few topics concerning the early chemical evolution of the Milky Way are critically discussed. In particular, it is argued that: 1) Observed abundance patterns of extremely metal poor stars (of Pop. II) do not constrain the mass range of…
We examine the role of rotation on the evolution and chemical yields of very metal--poor stars. The models include the same physics, which was applied successfully at the solar $Z$ and for the SMC, in particular, shear diffusion, meridional…
The early chemical evolution of the Galaxy and the Universe is vital to our understanding of a host of astrophysical phenomena. Since the most metal-poor Galactic stars (with metallicities down to [Fe/H]\sim-5.5) are relics from the…
We have investigated chemical evolution in the young universe by analysing the detailed chemical enrichment pattern of a metal-rich galaxy at high redshift. The recent detection of over 20 elements in the gas-phase of a damped Lyman-alpha…
Rotating massive stars at $Z=10^{-8}$ and $10^{-5}$ lose a great part of their initial mass through stellar winds. The chemical composition of the rotationally enhanced winds of very low $Z$ stars is very peculiar. The winds show large CNO…
After a review of the many effects of metallicity on the evolution of rotating and non-rotating stars, we discuss the consequences of a high metallicity on massive star populations and on stellar nucleosynthesis. The most striking effect of…
Motivated by the WMAP results indicating an early epoch of reionization, we consider alternative cosmic star formation models which are capable of reionizing the early intergalactic medium. We develop models which include an early burst of…
At metallicities lower than that of the Small Magellanic Cloud, it remains essentially unexplored how fossil magnetic fields, forming large-scale magnetospheres, could affect the evolution of massive stars, thereby impacting the fundamental…
Recently, measurements of abundances in extremely metal poor (EMP) stars have brought new constraints on stellar evolution models. In an attempt to explain the origin of the abundances observed, we computed pre--supernova evolution models,…
I present a new Galactic chemical evolution model motivated by and grounded in the hierarchical theory of galaxy formation, as expressed by a halo merger history of the Galaxy. This model accurately reproduces the "metallicity distribution…
Context. Carbon, nitrogen, and oxygen are the most abundant elements throughout the universe, after hydrogen and helium. Studying these elements in low-metallicity stars can provide crucial information on the chemical composition in the…
We apply a physically motivated stellar feedback model to analyse the statistical properties of damped Lyman-alpha systems (DLAs) expected in the concordance cold dark matter (CDM) model. Our feedback model produces extended low-metallicity…
Recent observations by JWST have revealed supersolar $^{14}$N abundances in galaxies at very high redshift. On the other hand, these galaxies show subsolar metallicity. The observed N/O ratios are difficult to reproduce in the framework of…
The evolution of the metallicity of damped Lyman alpha systems (DLAs) is investigated in order to understand the nature of these systems. The observational data on chemical abundances of DLAs are analysed with robust statistical methods,…
In this paper, we investigate the star formation and chemical evolution of damped Lyman-$\alpha$ systems (DLAs) based on the disc galaxy formation model which is developed by Mo, Mao & White. We propose that the DLAs are the central…
We investigate the evolutionary history of the Universe's metal content focusing on the chemical abundance of several elements (N, O, S, Si, Fe, Cr, Zn) taken from observational data and predictions from chemical evolution models. The…
We study the evolutionary and physical properties of evolved O stars in the Small Magellanic Cloud (SMC), with a special focus on their surface abundances to investigate the efficiency of rotational mixing as a function of age, rotation and…