Related papers: Deuterium abundance and cosmology
The current picture painted by the observations of circumstellar dust at white dwarfs, and the consequent atmospheric pollution, is of a surviving planetary system. This chapter recounts in detail both the discovery and empirical…
White dwarf stars frequently experience external pollution by heavy elements, and yet the intrinsically carbon-enriched DQ spectral class members fail to exhibit this phenomenon, representing a decades-old conundrum. This study reports a…
There is no universally acknowledged criterion to distinguish brown dwarfs from planets. Numerous studies have used or suggested a definition based on an object's mass, taking the ~13-Jupiter mass (M_J) limit for the ignition of deuterium.…
We report the detection of Deuterium absorption at redshift 2.525659 towards Q1243+3047. We describe improved methods to estimate the Deuterium to Hydrogen abundance ratio (D/H) in absorption systems, including improved modeling of the…
We study the observed small deviations of high-redshift absorption spectra that are interpreted as a possible evidence for a variable fine structure constant. On the contrary, we claim that the effect could be completely attributed to the…
First results are presented for a Hubble Space Telescope Advanced Camera for Surveys snapshot study of white dwarfs with likely red dwarf companions. Of 48 targets observed and analyzed so far, 27 are totally or partially resolved into two…
The importance of HST for the study of quasar absorption lines and of the nature of the intergalactic medium is illustrated by reviewing selected results from past HST observations. Topics reviewed include the study of Ly-alpha absorbers at…
Abundance histories for QSO absorption line systems as a function of redshift are presented for all metals lighter than gallium. Coupling various conventional cosmological models with a simple, first--order model for the chemical evolution…
The precision cosmological model describing the origin and expansion history of the universe, with observed structure seeded at the inflationary cosmic horizon, demands completion in the ultraviolet and in the infrared. The dynamics of the…
By using a Reverse Monte Carlo technique aimed at the inverse problem in the analysis of the H+D Ly-a absorption from QSO spectra we have estimated the physical parameters of the gas and the large-scale line of sight velocity structure…
Quasar (or QSO) elemental abundances provide unique probes of high-redshift star formation and galaxy evolution. There is growing evidence from both the emission and intrinsic absorption lines that QSO environments have roughly solar or…
This chapter provides an in-depth overview of white dwarfs, the evolutionary terminus of the vast majority of stars. It discusses their discovery, their nature as degenerate objects, their connections to earlier phases of stellar evolution,…
We present a theoretical study of the deuterated species detectability in various types of extragalactic star-forming regions based on our predictions of chemical abundances. This work is motivated by the past and current attempts at…
Comparing Big Bang Nucleosynthesis predictions with the light element abundances inferred from observational data, we can obtain the strong constraints on some neutrino properties, e.g. number of neutrino species, mass, lifetime. Recently…
The determination of photospheric abundances in late-type stars from spectroscopic observations is a well-established field, built on solid theoretical foundations. Improving those foundations to refine the accuracy of the inferred…
White dwarfs are a class of stars with unique physical properties. They present many challenging problems whose solution requires the application of advanced theories of dense matter, state-of-the-art experimental techniques, and extensive…
Because the ionization balances for HI, OI, and DI are locked together by charge exchange, D/O is an important tracer for the value of the D/H ratio and for potential spatial variations in the ratio. As the DI and OI column densities are of…
This aims to be an overview of what detailed observations of individual stars in nearby dwarf galaxies may teach us about galaxy evolution. This includes some early results from the DART (Dwarf Abundances and Radial velocity Team) Large…
In this article we describe the search for white dwarfs (WDs) in the multi-band photometric data of the Capodimonte deep field survey. The WD candidates were selected through the V-R_C vs B-V color-color diagram. For two bright objects, the…
Observations of deuterated species are useful in probing the temperature, ionization level, evolutionary stage, chemistry, and thermal history of astrophysical environments. The analysis of data from ALMA and other new telescopes requires…