相关论文: Ionizing radiation fluctuations and large-scale st…

Hydrodynamic cosmological simulations predict that the average opacity of the Ly-alpha forest should increase in the neighborhood of galaxies because galaxies form in dense environments. Recent observations (Adelberger et al. 2002) confirm…

It appears inevitable that reionization processes would have produced large-scale temperature fluctuations in the intergalactic medium. Using toy temperature models and detailed heating histories from cosmological simulations of HeII…

We use Southern African Large Telescope (SALT) to perform long-slit spectroscopic observations of 23 newly discovered radio-loud quasars (RLQs) at $2.7<z<3.3$. The sample consists of powerful AGN brighter than 200 mJy at 1.4 GHz and is…

The high-redshift Universe contains luminous Lyman Alpha (hereafter Lya) emitting sources such as galaxies and quasars. The emitted Lya radiation is often scattered by surrounding neutral hydrogen atoms. We show that the scattered Lya…

We investigate the evolution and the statistical properties of the Lya absorbers of the intergalactic medium (IGM) in the largely unexplored redshift range z=0.5-1.9. We use high-resolution (R > 30,000) UV (STIS) and optical (VLT/UVES and…

The Lyman-$\alpha$ forest opacity fluctuations observed from high-redshift quasar spectra have been proven to be extremely successful in order to probe the late phase of the reionization epoch. For ideal modeling of these opacity…

We present 3D resonant radiative transfer simulations of the spatial and spectral diffusion of the Lya radiation from a central source in the host galaxies of high column density absorption systems at z ~ 3. The radiative transfer…

Further investigation of data on quasars, especially in the ultraviolet band, yields an amazingly coherent narrative which we present in this paper. Quasars are characterised by strong continuum emission and redshifted emission and…

We present a study of the Ly\alpha forest at z<0.4 from which we conclude that at least 20% of the total baryons in the universe are located in the highly-ionized gas traced by broad Ly\alpha absorbers. The cool photoionized low-z…

We use a new method to model fluctuations of the Lyman-Werner (LW) and Lyman-alpha radiation backgrounds at high redshift. At these early epochs the backgrounds are symptoms of a universe newly lit with its first stars. LW photons…

(Abridged) Aims. To probe the spectral energy distribution (SED) of the ionizing background radiation at z ~ 2 and to specify the sources contributing to the intergalactic radiation field. Methods. The spectrum of a bright quasar…

The amplitude of the metagalactic ultraviolet background (UVB) at large-scales is impacted by two factors. First, it naturally attenuates at scales larger than mean-free-path of UVB photons due to the absorption by neutral intergalactic…

A variety of independent observational studies have now reported a significant decline in the fraction of Lyman-break galaxies which exhibit Ly-a emission over the redshift interval z=6-7. In combination with the strong damping wing…

Quasars contribute to the 21-cm signal from the Epoch of Reionization (EoR) primarily through their ionizing UV and X-ray emission. However, their radio continuum and Lyman-band emission also regulates the 21-cm signal in their direct…

The lifetime of quasars can be estimated by means of their proximity zone sizes, which are regions of enhanced flux bluewards of the Lyman-$\alpha$ emission line observed in the rest-frame UV spectra of high-redshift quasars, because the…

We have constructed a sample of 29 close projected quasar pairs where the background quasar spectrum reveals absorption from optically thick HI gas associated with the foreground quasar. These unique sightlines allow us to study the quasar…

Quasars and active galactic nuclei (AGN) are significant contributors to the metagalactic ionizing background at redshifts z < 3. Recent HST/COS composite spectra of AGN find a harder flux distribution in the Lyman continuum, F_nu ~…

Ly$\alpha$ emission nebulae are ubiquitous around high-z galaxies and are tracers of the gaseous environment on scales out to >100 kpc. High-z radio galaxies (HzRGs, type-2 radio-loud quasars) host large scale nebulae observed in the…

With close pairs of quasars at different redshifts, a background quasar sightline can be used to study a foreground quasar's environment in absorption. We use a sample of 650 projected quasar pairs to study the HI Lya absorption transverse…

We present the BOSS Lyman-alpha (Lya) Forest Sample from SDSS Data Release 9, comprising 54,468 quasar spectra with zqso > 2.15 suitable for Lya forest analysis. This data set probes the intergalactic medium with absorption redshifts 2.0 <…