Related papers: Evolution of Deuterium, 3He and 4He in the Galaxy
In this work we present the predictions of a modified version of the ``two-infall model'' (Chiappini et al. 1997) for the evolution of 3He, 4He and D in the solar vicinity, as well as their distributions along the Galactic disk. In…
The uncertainties which still plague our understanding of the evolution of the light nuclides D, 3He and 4He in the Galaxy are described. Measurements of the local abundance of deuterium range over a factor of 3. The observed dispersion can…
The predictions of Galactic chemical evolution models for D and $^3$He are described in connection with those on the other Galactic quantities for which observational constraints are available. Models in agreement with the largest set of…
New stellar models which track the production and destruction of $^3$He (and D) have been evolved for a range of stellar masses $(0.65\leq M/M_{\odot}\leq 100)$, metallicities $(0.01 \leq Z/Z_{\odot} \leq 1)$ and initial (main sequence)…
The primordial abundances of deuterium and of helium-3, produced during big bang nucleosynthesis, depend sensitively on the baryon density. Thus, the observed abundances of D and \he may provide useful ``baryometers'' provided the evolution…
(Abridged) Estimates of the interstellar deuterium abundance span a wide range of values. Here we study the evolution of deuterium in the framework of successful models for the chemical evolution of the Milky Way able to reproduce the…
Chemical features of the local stellar disk have firmly established that long-term, continuous star formation has been accompanied by a steady rate of accretion of low-metallicity gas from the halo. We now argue that the recent discovery of…
To understand the chemical evolution of the Galaxy, we need to understand the contribution of PNe in the 3He abundance. 3He abundances have been detected only in a couple of PNe, their abundances are consistent with the standard models, in…
Recent studies of low- and intermediate-mass stars show that the evolution of the chemical elements in these stars is very different from that proposed by standard stellar models. Rotation-induced mixing modifies the internal chemical…
We report on measurements of the 4He abundance toward the outer Galaxy HII region S206 with the NRAO Green Bank telescope. Observations of hydrogen and helium radio recombination lines between 8-10 GHz were made toward the peak radio…
Galactic destruction of primordial deuterium is inevitably linked through star formation to the chemical evolution of the Galaxy. The relatively high present gas content and low metallicity suggest only modest D-destruction. In concert with…
Measurements of deuterium in the local interstellar medium have revealed large variations in D/H along different lines of sight. Moreover, recent {\it Far Ultraviolet Spectroscopic Explorer} (FUSE) measurements find D/H to be anticorrelated…
Two aspects of the chemical evolution of 4He in the Galaxy are considered on the basis of a sample of disk planetary nebulae by the application of corrections due to the contamination of 4He from the progenitor stars. First, the He/H radial…
In this work, two aspects of the chemical evolution of 4He in the Galaxy are considered on the basis of a sample of disk planetary nebulae (PN). First, an application of corrections owing to the contamination of 4He from the evolution of…
The determined abundances of primordial $^4He$ and $^7Li$ provide a basis with which to test the standard model of big bang nucleosynthesis in conjunction with the other two light element isotopes $D$ and $^3He$, also produced in the big…
We consider the galactic evolutionary history of \he3 in models which deplete deuterium by as much as a factor of 2 to $\sim$ 15 from its primordial value to its present day observed value in the ISM. We show that when \he3 production in…
We reanalyze the inference of the protosolar abundance of deuterium made by Geiss (1993) from measurements of 3He/4He in the solar wind. We use an evolutionary solar model with microscopic diffusion, constrained to fit the present age,…
The total deuterium abundance [D/H] in the universe is set by just two processes: the creation of deuterium in Big Bang Nucleosynthesis at an abundance of [D/H]$=2.58\pm0.13\times10^{-5}$, and its destruction within stellar interiors.…
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)…
We discuss the chemical evolution of dwarf irregular and blue compact galaxies in light of recent data, new stellar yields and chemical evolution models. We examine the abundance data for evidence of HII region self-enrichment effects,…