Related papers: The Connections between QSO Absorption Systems and…
A small survey of the UV-absorbing gas in 12 low-$z$ galaxy groups has been conducted using the Cosmic Origins Spectrograph (COS) on-board the Hubble Space Telescope (HST). Targets were selected from a large, homogeneously-selected sample…
We present an investigation of the properties of the extended Ly$\alpha$ halo and the large-scale \ion{H}{I} absorbing structures associated with 5 high-redshift radio galaxies at z $>$ 2, using the Goodman long-slit spectrograph on the…
Using Hubble Space Telescope Cosmic Origins Spectrograph observations of 89 QSO sightlines through the Sloan Digital Sky Survey footprint, we study the relationships between C IV absorption systems and the properties of nearby galaxies as…
The aim of this project is to identify low-redshift host galaxies of quasar absorption-line systems by selecting galaxies which are seen in projection onto quasar sightlines. To this end, we use the Seventh Data Release of the Sloan Digital…
We present a new method to study the contribution of faint sources to the UV background using the 1D correlation of metal absorbers with the intergalactic medium (IGM) transmission in a Quasi Stellar Object (QSO) sightline. We take…
We present a new method for probing the physical conditions and metal enrichment of the Intergalactic Medium: the composite spectrum of Ly-alpha forest absorbers. We apply this technique to a sample of 9480 Ly-alpha absorbers with redshift…
Radio wave propagation can be perturbed by compact ionized gas clumps through plasma lensing, which induces frequency dependent magnification and may distort the observed number counts of background sources. The quasar (QSO) number…
We report Hubble Space Telescope Cosmic Origins Spectrograph far-ultraviolet and Arecibo Telescope H{\sc i} 21cm spectroscopic studies of six damped and sub-damped Lyman-$\alpha$ absorbers (DLAs and sub-DLAs, respectively) at $z \lesssim…
A comprehensive set of all available magnitudes, colors and redshifts for optically identified QSO absorbers is compiled from the literature. This results in a largely unbiased sample of galaxies at high redshifts, the size of the sample…
HI-rich absorbers seen within quasar spectra contain the bulk of neutral gas in the Universe. However, the spatial extent of these reservoirs are not extensively studied due to the pencil beam nature of quasar sightlines. Using two giant…
We present an analysis of the galaxy environment and physical properties of a partial Lyman limit system at z = 0.83718 with HI and metal line components closely separated in redshift space ($|\Delta v| \approx 400$ km/s) towards the…
Radio-selected samples of quasars with complete optical identifications offer an ideal dataset with which to investigate dust bias associated with intervening absorption systems. Here, we review our work on the Complete Optical and Radio…
We present further observational results on our Lya-only absorber identification project at low and intermediate redshifts. We combine CFHT/MOS imaging and spectroscopic observations of 25 galaxies in the field of the quasar 3C286 (z_e =…
Galaxy halos appear to be missing a large fraction of their baryons, most probably hiding in the circumgalactic medium (CGM), a diffuse component within the dark matter halo that extends far from the inner regions of the galaxies. A…
Spectroscopy of high-redshift compact steep-spectrum (CSS) quasars shows a high incidence of Ly-alpha absorption close to the quasar redshift. Associated absorption systems like these are rare in other types of radio sources, with the…
Galaxies are surrounded by large reservoirs of gas, mostly hydrogen, fed by inflows from the intergalactic medium and by outflows due to galactic winds. Absorption-line measurements along the sightlines to bright and rare background quasars…
Determining when and how the first galaxies reionized the intergalactic medium (IGM) promises to shed light on both the nature of the first objects and the cosmic history of baryons. Towards this goal, quasar absorption lines play a unique…
We report {\it HST} COS spectroscopy of 10 quasars with foreground star-forming galaxies at 0.02$<$$z$$<$ 0.14 within impact parameters of $\sim$1-7 kpc. We detect damped/sub-damped Ly$\alpha$ absorption in 100$\%$ of cases where no…
The presence of a ``warm absorber'' was first suggested to explain spectral variability in an X-ray spectrum of the radio-quiet QSO MR2251-178. A unified picture, in which X-ray warm absorbers and ``intrinsic'' UV absorbers are the same,…
This paper addresses the global molecular gas properties of a representative sample of galaxies hosting low-luminosity quasistellar objects. An abundant supply of gas is necessary to fuel both the active galactic nucleus and any…