Related papers: What's The Problem With ^3He?
We investigate the influence of the initial proto-galaxies over-densities and masses on their evolution, to understand whether the internal properties of the proto-galactic haloes are sufficient to account for the varied properties of the…
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,…
Population III stars supplied the first light and metals in the Universe, setting the pace of re-ionisation and early chemical enrichment. In dense haloes their evolution can be strongly influenced by the energy released when WIMPs…
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…
We used the VLA to search for 3He+ emission from two Galactic planetary nebulae (PNe): NGC6572 and J320}. Standard stellar models predict that the 3He/H abundance ratios for PNe should be 1-2 orders of magnitude higher than the primordial…
In recent years several hypervelocity stars (HVSs) have been observed in the halo of our Galaxy. Such stars are thought to be ejected through dynamical interactions near the massive black hole (MBH) in the Galactic center. Three scenarios…
The abundance patterns of extremely metal-poor stars preserve a fossil record of the Universe's earliest chemical enrichment by the supernova explosions from the evolution of first generation of stars, also referred to as Population III (or…
Motivated by recent theoretical work suggesting that a substantial fraction of Population (Pop) III stars may have had masses low enough for them to survive to the present day, we consider the role that the accretion of metal-enriched gas…
Accurate measurements of interstellar deuterium abundances along lines of sight extending out to several hundred parsecs by FUSE and other instruments is making D/H a useful tool for understanding Galactic chemical evolution. We find that…
We present new upper and lower bounds to the primordial abundances of deuterium and helium-3 based on observational data from the solar system and the interstellar medium. Independent of any model for the primordial production of the…
Deuteration is sensitive to environmental conditions in star-forming regions. To investigate NH$_2$D chemistry, we compared the spatial distribution of ortho-NH$_2$D $1_{11}^s-1_{01}^a$, NH$_3$(1,1) and NH$_3$(2,2) in 12 late-stage massive…
Precise studies on the Galactic bulge, halo, thick disk, and globular clusters require stellar models with alpha enhancement and various He contents. For this purpose we complement existing PARSEC (PAdova-TRieste Stellar Evolution Code)…
We present a semi-analytic, computationally inexpensive model to identify halos capable of forming a Population III star in cosmological simulations across a wide range of times and environments. This allows for a much more complete and…
We use the scatter in the stellar-to-halo mass relation to constrain galaxy evolution models. If the efficiency of converting accreted baryons into stars varies with time, halos of the same present-day mass but different formation histories…
Observations of quasar absorption line systems reveal that the z=3 intergalactic medium (IGM) is polluted by heavy elements down to HI optical depths tau_HI<<10. What is not yet clear, however, is what fraction of the volume needs to be…
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.…
We report on a survey of \nh2d towards protostellar cores in low-mass star formation and quiescent regions in the Galaxy. Twenty-three out of thirty-two observed sources have significant ($\gsim 5\sigma$) \nh2d emission. Ion-molecule…
The success of primordial nucleosynthesis has been limited by the long-standing Lithium problem. We use a self-consistent perturbative analysis of the effects of relevant theoretical parameters on primordial nucleosynthesis, including…
Several B-type main-sequence stars show chemical peculiarities. A particularly striking class are the $^3$He stars, which exhibit a remarkable enrichment of $^3$He with respect to $^4$He. This isotopic anomaly has also been found in blue…
Low-mass stars, ~1-2 solar masses, near the Main Sequence are efficient at producing 3He, which they mix into the convective envelope on the giant branch and distribute into the Galaxy by way of envelope loss. This process is so efficient…