相关论文: Cosmic Star Formation, Reionization, and Constrain…
This paper presents the first results from a model for chemical evolution that can be applied to N-body cosmological simulations and quantitatively compared to measured stellar abundances from large astronomical surveys. This model…
Using a new numerical model for cosmic chemical evolution, we study the influence of hypernova feedback on the star formation and metal enrichment history of the universe. For assumptions which produce plausible results in idealized…
We present preliminary results of stellar structure and nucleosynthesis calculations for some early stars. The study (still in progress) seeks to explore the expected chemical signatures of second generation low- and intermediate-mass stars…
This work studies the connection between the first galaxies and their hosting dark matter halos in the early Universe when Reionization is concluding. Our numerical models (already presented in an earlier study) trace the star formation…
We calculate the contribution to the cosmic infrared background from very massive metal-free stars at high redshift. We explore two plausible star-formation models and two limiting cases for the reprocessing of the ionizing stellar…
We critique the hypothesis that the first stars were very massive stars (VMS; M > 140 Msun). We review the two major lines of evidence for the existence of VMS: (1) that the relative metal abundances of extremely metal-poor Galactic halo…
We investigate the impact of an early population of massive stars on their surroundings. Dissociation of molecular hydrogen by strong UV emission from such stars is expected to produce a global transition in the cooling mechanism of…
The WMAP satellite has measured a large optical depth to electron scattering after cosmological recombination of 0.17+-0.04, implying significant reionization of the primordial gas only ~200 million years after the big bang. However, the…
The reionization of cosmic hydrogen marks a critical juncture in the history of structure formation in the universe. Here we present a new formulation of the standard reionization equation for the evolution of the volume-averaged HII…
A model for Galactic chemical evolution, driven by supernova-induced star formation, is formulated and used to examine the nature of the Galactic halo at early epochs. In this model, new stars are formed following each supernova event, thus…
We calculate the reionization history for different models of the stellar population and explore the effects of primordial magnetic fields, dark matter decay and dark matter annihilation on reionization. We find that stellar populations…
We reanalyze the photoevaporation problem of subgalactic objects irradiated by UVB radiation in a reionized universe. For the purpose, we perform three-dimensional radiation smoothed-particle-hydrodynamics calculations, where the radiative…
Recent studies of heavy r-process elements in low [Fe/H] halo stars have suggested that an initial population of metal-free very massive stars (VMSs) may be required to provide early Fe enrichment without coproducing heavy r nuclei. We find…
Over the past decade increasingly robust estimates of the dense molecular gas content in galaxy populations between redshift 0 and the peak of cosmic galaxy/star formation from redshift 1-3 have become available. This rapid progress has…
Dark stars powered by dark matter annihilation have been proposed as the first luminous sources in the universe. These stars are believed to form in the central dark matter cusp of low-mass minihalos. Recent calculations indicate stellar…
The early reionization of the intergalactic medium, which is favored from the WMAP temperature-polarization cross-correlations, contests the validity of the standard scenario of structure formation in the cold dark matter cosmogony. It is…
We examine the cosmic evolution of a stellar initial mass function (IMF) in galaxies that varies with the Jeans mass in the interstellar medium, paying particular attention to the K-band stellar mass to light ratio (M/L_K) of present-epoch…
I review recent observational and theoretical progress in our understanding of the cosmic evolution of luminous sources. Largely due to a combination of deep HST imaging, Keck spectroscopy, and COBE far-IR background measurements, new…
In this paper the role of very massive pop III stars in the chemical enrichment of the early universe is discussed. We first compare our predictions with the abundance ratios measured in the high redshift Lyman-alpha forest to check whether…
Recent results by the WMAP satellite suggest that the intergalactic medium was significantly reionized at redshifts as high as z~17. At this early epoch, the first ionizing sources likely appeared in the shallow potential wells of…