Related papers: The ionizing background at the end of overlap
Since the photons that stream from QSOs alter the ionization state of the gas they traverse, any changes to a QSO's luminosity will produce outward-propagating ionization gradients in the surrounding intergalactic gas. This paper shows that…
We present the analysis of deep HST multi-band imaging of the BDF field specifically designed to identify faint companions around two of the few Ly-alpha emitting galaxies spectroscopically confirmed at z~7 (Vanzella et al. 2011). Although…
We study the reionization scenario in which ionizing UV photons emitted from decaying particle, in addition to usual contributions from stars and quasars, ionize the universe. It is found that the scenario is consistent with both the first…
We reassess constraints on the cosmological baryon density from observations of the mean decrement and power spectrum of the Lyman-alpha forest, taking into account uncertainties in all free parameters in the simplest gravitational…
With the recent measurement of full sky cosmic microwave background polarization from WMAP, key cosmological degeneracies have been broken, allowing tighter constraints to be placed on cosmological parameters inferred assuming a standard…
We investigate the thermal and ionization history of Lyman alpha clouds photoionized by a time--dependent UV background, including non equilibrium effects. The results show that it is possible to obtain temperatures as low as T~15000 K (or,…
It is shown that, in addition to the Thomson scattering, the absorption due to the electron-electron, electron-ion and the electron -atom collisions in a partially ionized cosmic plasma would also contribute to the optical depth of the…
We show the universe was reionized twice, first at z~15-16 and second at z~6. Such an outcome appears inevitable, when normalizing to two well determined observational measurements, namely, the epoch of the final cosmological reionization…
We present measurements of the mean and scatter of the IGM Lyman-{\alpha} opacity at 4.9 < z < 6.1 along the lines of sight of 62 quasars at z > 5.7, the largest sample assembled at these redshifts to date by a factor of two. The sample…
We describe an ongoing experiment to search for the meta-galactic Lyman-continuum background at z~2-3. We are obtaining one of the deepest optical spectra ever, using LRIS/Keck-II to search for the fluorescent Ly-alpha emission from…
Interpretation of He II Ly{\alpha} absorption spectra after the epoch of He II reionization requires knowledge of the He II ionizing background. While past work has modelled the evolution of the average background, the standard cosmological…
We present constraints on the cosmological and reionization parameters based on the cumulative mass function of the Ly-alpha systems. We find that the analysis of the cumulative mass function of the Ly-alpha systems indicates a reionization…
The intergalactic medium (IGM) around quasars is shaped by their dense environments and by their excess ionizing radiation, forming a "quasar proximity zone" whose size and anisotropy depend on the quasar's halo mass, luminosity, age, and…
We present the first results from our survey of intervening and proximate Lyman limit systems (LLSs) at $z$$\sim$2.0-2.5 using the Wide Field Camera 3 on-board the Hubble Space Telescope. The quasars in our sample are projected pairs with…
The distribution of diffuse gas in the intergalactic medium (IGM) imprints a series of hydrogen absorption lines on the spectra of distant background quasars known as the Lyman-$\alpha$ forest. Cosmological hydrodynamical simulations…
The first galaxies to appear in the universe at redshifts z>20 created ionized bubbles in the intergalactic medium of neutral hydrogen left over from the Big-Bang. It is thought that the ionized bubbles grew with time, surrounded clusters…
We model the transmission of the Lyman-alpha line through the circum- and intergalactic media around dark matter haloes expected to host Lyman-alpha emitters (LAEs) at z > 5.7, using the high-dynamic-range Sherwood simulations. We find very…
We present the largest-ever sample of 79 Ly$\alpha$ emitters (LAEs) at $z\sim$ 7.0 selected in the COSMOS and CDFS fields of the LAGER project (the Lyman Alpha Galaxies in the Epoch of Reionization). Our newly amassed ultradeep narrowband…
The fraction of galaxies with strong Ly$\alpha$ emission has been observed to decrease rapidly with redshift at $z \ge 6$, after a gradual increase at $z< 6$. This has been interpreted as a hint of the reionization of the intergalactic…
We investigate the implications of our measurement of the Lyman-alpha forest opacity at redshifts 2<z<4.2 from a sample of 86 high-resolution quasar spectra for the evolution of the cosmic ultraviolet luminosity density and its sources. The…