相关论文: Radiation Pressure in Lyman-alpha Forest Clouds
We have performed a multi-species hydrodynamical simulation of the formation and evolution of Lyman alpha clouds in a flat CDM dominated universe with an external flux of ionizing radiation. We solve the fully coupled non-equilibrium rate…
We perform Lyman-alpha radiative transfer calculations for reproducing Lyman-alpha properties of star-forming galaxies at high redshifts. We model a galaxy as a halo in which the density distributions of Lyman-alpha sources and H I plus…
Using radiative transfer calculations and cosmological simulations of structure formation, we study constraints that can be placed on the nature of the cosmic ultraviolet (UV) background in the redshift interval 2.5< z <5. Our approach…
A break in the distribution function of Ly$\alpha$ clouds (at a typical redshift of $2.5$) has been reported by Petitjean et al. (1993). This feature is what would be expected from a transition between pressure confinement and gravity…
The influence of a foreground QSO on the lyman a forest of another QSO with higher redshift has been investigated by analyzing the spectra of three such objects at redshifts $z=2 - 2.7$. This influence is not contaminated by any projection…
We present a measurement of the Lyman alpha flux probability distribution function (PDF) measured from a set of eight high resolution quasar spectra with emission redshifts at 3.3 < z < 3.8. We carefully study the effect of metal absorption…
We present results from high resolution (R\simeq 28000) spectra of six high- redshift QSOs taken at the ESO NTT telescope that allow the detailed study of the Ly-alpha population in the redshift interval z=2.8-4.1. The typical Doppler…
The spectrum of cosmic ultraviolet background radiation at He II ionizing energies (E > 4 Ryd) is important to study the He II reionization, thermal history of the intergalactic medium (IGM) and metal lines observed in QSO absorption…
In the low density intergalactic medium (IGM) that gives rise to the Lyman-alpha forest, gas temperature and density are tightly correlated. The velocity scale of thermal broadening and the Hubble flow across the gas Jeans scale are of…
We study the evolution with redshift of the number density of Ly$\alpha$ clouds in a CDM model using numerical simulations including photo-ionization and cooling of the baryonic component. The photo-ionizing flux is consistently taken as…
Cosmological simulations with gas provide a detailed description of the intergalactic medium, making possible predictions of neutral hydrogen absorption in the spectra of background QSOs. We present results from a high-resolution…
The analysis of the Lyman-alpha forest of absorption lines in quasar spectra has emerged as a potentially powerful technique to constrain the linear matter power spectrum. In most previous work, the amplitude of the ionizing background was…
Models are presented for the Lyman alpha emission of dusty high-redshift galaxies by combining the Press-Schechter formalism with a treatment of the inhomogeneous dust distribution inside galaxies. It is found that the amount of Lyman alpha…
When modelling the ionisation of gas in the intergalactic medium after reionisation, it is standard practice to assume a uniform radiation background. This assumption is not always appropriate; models with radiative transfer show that…
We show that comparisons of HeII Lyman-alpha forest lines of sight to nearby quasar populations can strongly constrain the lifetimes and emission geometry of quasars. By comparing the HeII and HI Lyman-alpha forests along a particular line…
In this article, the temperature-density relation of the intergalactic medium was studied in the region $1.6 \leq z < 2.0$ divided into two bins. For this purpose, the Ly-$\alpha$ forest decomposition into individual absorption profiles was…
We use the probability distribution function (PDF) of the lya forest flux at z=2-3, measured from high-resolution UVES/VLT data, and hydrodynamical simulations to obtain constraints on cosmological parameters and the thermal state of the…
Cosmological constraints from the cosmic microwave background (CMB) anisotropies rely on accurate theoretical calculations of the cosmic recombination history. Recent work has emphasized the importance of radiative transfer calculations due…
We have re--examined the chemical composition of \lya clouds using the composite--cloud technique, in which each \lya line in a spectrum is shifted to its rest frame wavelength and all rest frame spectra are co--added to form an `averaged'…
Many experts believe that the z ~ 3 HeII Ly-alpha forest will suffer from the same saturation issues as the z ~ 6 HI Ly-alpha forest and, therefore, will not be a sensitive probe of HeII reionization. However, there are several factors that…