▪ Abstract Observations of redshifted Lyman α (Lyα) forest absorption in the spectra of
quasistellar objects (QSOs) provide a highly sensitive probe of the distribution of gaseous …

Determining when and how the first galaxies reionised the intergalactic medium promises to
shed light on both the nature of the first objects and the cosmic history of baryons. Towards …

Bearing on the model for the time-dependent metagalactic radiation field developed in the
first paper of this series, we compute the gamma-ray attenuation due to pair production in …

Galaxies and quasars are thought to provide the bulk of the photons responsible for ionizing
the hydrogen in the intergalactic medium (IGM). We use a large set of hydrodynamical …

We have measured the distribution function of the flux decrement D= 1-e-τ caused by Ly α
forest absorption from intervening gas in the lines of sight to high-redshift QSOs from a …

We present a measurement of the deuterium to hydrogen ratio (D/H) in a metal-poor
absorption system at redshift z= 2.504 toward the QSO 1009+ 2956. We apply the new …

We investigate the implications of the intergalactic opacity for the evolution of the cosmic UV
luminosity density and its sources. Our main constraint is our measurement of the Lyα forest …

We derive lower bounds on the cosmic baryon density from the requirement that the high-
redshift intergalactic medium (IGM) contain enough neutral hydrogen to produce the …

We use ultra-deep ultraviolet VLT/VIMOS intermediate-band and VLT/FORS1 narrowband
imaging in the GOODS Southern field to derive limits on the distribution of the escape …

Gamma-ray absorption due to-pair creation on cosmological scales depends on the line-of-
sight integral of the evolving density of low-energy photons in the Universe, ie on the history …