Related papers: Measuring Omega Baryon from the Helium Lyman-Alpha…
The primordial D/H ratio now provides the best measure of the cosmological density of baryons. We describe in detail how we deduce the D/H ratio from absorption lines in the spectra of quasars, and we present our first two measurements of…
We propose to infer ionising continuum leaking properties of galaxies by looking at their Lyman-alpha line profiles. We carry out Lyman-alpha radiation transfer calculations in two models of HII regions which are porous to ionising…
We present some statistical features of the large number of \lya absorption lines detected in high redshift quasar spectra, obtained by using the multifractal approach. In the analysed sample of 12 QSO sight--lines, 11 show scaling…
We present a detection of a broad Ly-alpha absorber (BLA) with a matching O VI line in the nearby universe. The BLA is detected at z = 0.01028 in the high S/N spectrum of Mrk 290 obtained using the Cosmic Origins Spectrograph. The Ly-alpha…
We introduce a new statistic omega_l for measuring and analyzing large-scale structure and particularly the baryon acoustic oscillations. omega_l is a band-filtered, configuration space statistic that is easily implemented and has…
Detecting HI using redshifted Ly-alpha absorption lines is 1e6 times more sensitive than using the 21cm emission line. We review recent discoveries of HI Ly-alpha absorbers made with the Hubble Space Telescope (HST) which have allowed us a…
Baryon Acoustic Oscillations (BAO) datasets use very precise measurements of the spatial distribution of large-scale structures as a distance ladder to help constrain cosmological parameters. In a recent article \cite{Benisty:2020otr}, we…
The discovery of a z_abs = 0.0912 damped Lyman-alpha absorption-line system in the HST-FOS ultraviolet spectrum of the quasar OI 363 (0738+313) is reported. This is the lowest redshift quasar damped Lyman-alpha system known. Its neutral…
The spectra of the first galaxies and quasars in the Universe should be strongly absorbed shortward of their rest-frame Lyman-alpha wavelength by neutral hydrogen (HI) in the intervening intergalactic medium. However, the Lyman-alpha line…
One of the outstanding problems of current observational cosmology is to understand the nature of sources that produced the bulk of the ionizing radiation after the Cosmic Dark Age. Direct detection of these reionization sources is…
We describe a moderate-resolution (20-25 km/s) FUSE study of the low-redshift intergalactic medium. We report on studies of 7 extragalactic sightlines and 12 Ly-beta absorbers that correspond to Ly-alpha lines detected by HST/GHRS and STIS.…
We report a deep radio search with the Ooty Radio Telescope (ORT) for the redshifted 21 cm absorption line from the damped Lyman alpha system seen at redshift 3.388 against the quasar PKS 0201+113. This is currently the most distant system…
The hydrogen Ly$\alpha$ forest is an important probe of the $z>2$ Universe that is otherwise challenging to observe with galaxy redshift surveys, but this technique has traditionally been limited to 1D studies in front of bright quasars.…
We present new measurements of the mean transmitted flux in the hydrogen Ly$\rm \alpha$ and a relative transmitted flux measurement in Ly$\rm \beta$ using 27,008 quasar spectra from the Fourteenth Data Release (DR14) of the Extended Baryon…
As part of a larger program to identify low redshift radio analogues of the damped Lyman-alpha (DLA) absorbers seen in the spectra of high redshift quasars, Westerbork Synthesis Radio Telescope (WSRT) observations have discovered two new HI…
Lyman-alpha forest lines in QSO spectra have typical widths of 20-50 km/s. Low column density absorbers in cosmological simulations are large, diffuse structures, and the Hubble flow across the spatially extended absorber is usually the…
We describe recent discoveries of low column density [N(HI) < 10^14.5 cm^-2] H I Ly-alpha absorbers made with the Hubble Space Telescope (HST), which have allowed us a first look at gas in local intergalactic space between us and the "Great…
We determine the product of the expansion rate and angular-diameter distance at redshift $z=2.3$ from the anisotropy of Lyman-$\alpha$ (Ly$\alpha$) forest correlations measured by the Sloan Digital Sky Survey (SDSS). Our result is the most…
We show that the high local baryonic fraction, M(bar) ~ 1/3 M(tot), found in groups and clusters of galaxies does not reconcile the observed cosmological baryon density with the standard Big-Bang prediction. Taking into account recent…
When measuring the one-dimensional power spectrum of the Ly$\alpha$ forest, it is common to measure the power spectrum in flux fluctuations red-ward of the Ly$\alpha$ emission of quasars and subtract this power from the measurements of the…