Related papers: Adenine Abundance in a Collapsing Molecular Cloud
In this paper we discuss some results concerning the abundance discrepancy problem in the context of H II regions. We discuss the behavior of the abundance discrepancy factor (ADF) for different objects and ions. There are evidences that…
The origin of cosmic dust is a fundamental issue in planetary science. This paper revisits the origin of dust in galaxies, in particular, in the Milky Way, by using a chemical evolution model of a galaxy composed of stars, interstellar…
Chemical tagging is a central pursuit of galactic archaeology, but requires sufficiently discriminative abundances to uniquely identify sites of star formation. This task is complicated by intrinsic scatter among conatal stars,…
Understanding the chemical evolution in star-forming cores is a necessary pre-condition to correctly assess physical conditions when using molecular emission. We follow the evolution of chemistry and molecular line profiles through the…
We present a theoretical investigation of the chemistry of fluorine-bearing molecules in diffuse and dense interstellar gas clouds. The chemistry of interstellar fluorine is qualitatively different from that of any other element, because -…
Recent observations reveal galaxies in the early Universe (2<z<6.4) with large reservoirs of molecular gas and extreme star formation rates. For a very large range of sources, a tight relationship exists between star formation rate and the…
Binary star systems are assumed to be co-natal and coeval, thus to have identical chemical composition. In this work we aim to test the hypothesis that there is a connection between observed element abundance patterns and the formation of…
Supernovae are expected to occur near the molecular material in which the massive progenitor star was born, except in cases where the photoionizing radiation and winds from the progenitor star and its neighbors have cleared out a region.…
(Abridged) We present the abundance analysis of 12 PNe ionized by [WC]-type stars and wels obtained from high-resolution spectrophotometric data. Our main aims are to determine the chemical composition of the PNe and to study the behaviour…
We consider the dynamical evolution of an interstellar cloud that is initially in thermal equilibrium in the warm phase and is then subjected to a sudden increase in the pressure of its surroundings. We find that if the initial plasma beta…
We study the formation of first molecules, negative Hydrogen ions and molecular ions in model of the Universe with cosmological constant and cold dark matter. The cosmological recombination is described in the framework of modified model of…
The deuterium abundances inferred from observations of the interstellar medium within 1-2 kpc of the Sun range over a factor of three and the corresponding oxygen abundances show an even larger dispersion. While the lower D (and O)…
To understand the formation and evolution of the Milky Way disk, we must connect its current properties to its past. We explore hydrodynamical cosmological simulations to investigate how the chemical abundances of stars might be linked to…
The time-delay model is the way we interpret the diagram [X/Fe] vs. [Fe/H], where X is the abundance of a generic element from carbon to uranium. This interpretation is based on the lifetimes of stars of different masses producing different…
The solar chemical composition is an important ingredient in our understanding of the formation, structure and evolution of both the Sun and our solar system. Furthermore, it is an essential reference standard against which the elemental…
The determination of accurate chemical abundances of planetary nebulae (PN) in different galaxies allows us to obtain important constraints of chemical evolution models for these systems. We have a long term program to derive abundances in…
Despite their shared origin, members of globular clusters display star-to-star variations in composition. The observed pattern of element abundances is unique to these stellar environments, and cannot be fully explained by any proposed…
We measure abundances of 12 elements (Na, Mg, Si, Ca, Sc, Ti, V, Cr, Mn, Fe, Co, Ni) in a sample of 86 metal-poor ($-2 \lesssim \text{[Fe/H]} \lesssim -1$) subgiant stars in the solar neighborhood. Abundances are derived from…
An analysis is made of the abundances of planetary nebulae (PN) in the Galaxy (MW), the Large Magellanic Cloud (LMC) and the Small Magellanic Cloud (SMC). The data has been gathered by the IAG/USP group in a homogeneous procedure, involving…
Planetary nebulae are the products of the evolution of low and intermediate mass stars. The chemical property studies of these objects give important information about the elemental abundances as He, O, Ne, Ar, S and their modifications…