相关论文: How exactly did the Universe become neutral?

The incorporation of radiative transfer effects into cosmological hydrodynamical simulations is essential for understanding how the intergalactic medium (IGM) makes the transition from a neutral medium to one that is almost fully ionized.…

During the era of primordial nucleosynthesis the light elements 2H, 3He, 4He, and 7Li were produced in significant amounts and these abundances have since been modified primarily by stars. Observations of 3He+ in HII regions located…

We develop and assess the potential of several powerful techniques, designed to investigate the details of reionization. First, we present a procedure to probe the neutral fraction, x_HI, using the Lyman alpha transmission statistics of…

The temporal evolution of the ionizing UV background radiation field at high redshift provides a probe of the evolution of the early star formation rate. By comparing the observed levels of absorption in the highest redshift quasar spectra…

We provide measurements of the neutral hydrogen fraction xHI at z~6, by comparing semi-analytical models of the Lyalpha forest with observations of high-z quasars and Gamma Ray Bursts absorption spectra. We analyze the transmitted flux in a…

In this paper we explore the potential effects of DM annihilations on the cosmological recombination spectrum. With this example we want to demonstrate that the cosmological recombination spectrum in principle is sensitive to details…

In this work we present a uniform analysis of the temperature evolution and bolometric luminosity of a sample of 29 type-II supernovae (SNe), by fitting a black body model to their multi-band photometry. Our sample includes only SNe with…

Helium ionization plays an important role in the energy balance of the upper chromosphere and transition region. Helium spectral lines are also often used as diagnostics of these regions. We carry out 1D radiation-hydrodynamics simulations…

Early reionization changes the pattern of anisotropies expected in the cosmic microwave background. To explore these changes, we derive from first principles the equations governing anisotropies, focusing on the interactions of photons with…

A one dimensional radiative transfer code is developed to track the ionization and heating pattern around the first miniquasars and Population III stars. The code follows the evolution of the ionization of the species of hydrogen and helium…

The recombination history of the Universe depends exponentially on the temperature, T_0, of the cosmic microwave background. Therefore tiny changes of T_0 are expected to lead to significant changes in the free electron fraction. Here we…

In the early universe, neutrinos decouple from equilibrium with the electromagnetic plasma at a temperature which is only slightly higher than the temperature where electrons and positrons annihilate. Therefore neutrinos to some extent…

In light of recent observations of spectra of the quasars SDSS 1030+0524 (Becker et al. 2001) and SDSS 1044-0125 (Djorgovski et al. 2001), we study the observational signatures of different stages of the reionization epoch. During the…

We obtained high-resolution VLT and FUSE spectra of the quasar HE2347-4342 to study the properties of the intergalactic medium between redshifts z=2.0-2.9. The high-quality optical spectrum allows us to identify approximately 850 HeII…

We investigate the possibility of maser amplification in hydrogen recombination lines from the galaxies of first generation, at z<~30. Combining analytical and computational approaches, we show that the transitions between the hydrogen…

In the framework of a quasi-molecular approach, the formation of hydrogen atom in the pre-recombination period of evolution of the universe is analysed quantitatively. Calculations in an adiabatic multi-level representation enable estimates…

Cosmological hydrogen recombination has recently been the subject of renewed attention because of its importance for predicting the power spectrum of cosmic microwave background anisotropies. It has become clear that it is necessary to…

The physical ingredients to describe the epoch of cosmological recombination are amazingly simple and well-understood. This fact allows us to take into account a very large variety of processes, still finding potentially measurable…

In this paper we refine the calculation of primordial helium recombination, accounting for several additional effects that were neglected or treated more approximately in previous studies. These include consideration of (i) time-dependent…

We update our prior work on the case B collisional-recombination spectrum of He I to incorporate \textit{ab initio} photoionisation cross-sections. This large set of accurate, self-consistent cross-sections represents a significant…