相关论文: Exploring the Damped Lyman-alpha Clouds with AXAF

We present a spectroscopic investigation with VLT/X-shooter of seven candidate extremely strong damped Lyman-$\alpha$ absorption systems (ESDLAs, $N(\text{HI})\ge 5\times 10^{21}$ cm$^{-2}$) observed along quasar sightlines. We confirm the…

We present a revised version of our automated technique using Gaussian processes (GPs) to detect Damped Lyman-$\alpha$ absorbers (DLAs) along quasar (QSO) sightlines. The main improvement is to allow our Gaussian process pipeline to detect…

Some pulsars have their maximum observable energy output in the gamma-ray band, offering the possibility of using these high-energy photons as probes of the particle acceleration and interaction processes in pulsar magnetospheres. After an…

We present a catalogue of absorption lines obtained from the analysis of the ultra-violet spectra of 66 quasars. The data were acquired with the Faint Object Spectrograph of the HST as part of the Quasar Absorption Line Survey, a Key…

We derive an analytic expression for the intensity of resonance-line radiation ``trapped'' in a semi-infinite medium. Given a source function and destruction probability per scattering, the radiation pressure due to trapped photons can be…

The last few years have seen a dramatic improvement in our understanding of the origin of Lyman alpha absorption systems. Hydrodynamic numerical simulations of cold dark matter dominated universes have shown that the many properties of the…

Determining the spatial distribution and intrinsic physical properties of neutral hydrogen on cosmological scales is one of the key goals of next-generation radio surveys. We use the EAGLE galaxy formation simulations to assess the…

In this paper we investigate the possible reasons why HI 21-cm absorption in damped Lyman-alpha systems (DLAs) has only been detected at low redshift... We suggest that the lack of 21-cm absorption detections at high redshift arises from…

We present a detailed analysis of a red quasar at z=2.32 with an intervening damped Lyman-alpha absorber (DLA) at z=2.13. Using high quality data from the X-shooter spectrograph at ESO Very Large Telescope we find that the absorber has a…

We have completed spectroscopic observations using LRIS on the Keck 1 telescope of 30 very high redshift quasars, 11 selected for the presence of damped Ly-alpha absorption systems and 19 with redshifts z > 3.5 not previously surveyed for…

X-ray Absorption Spectroscopy (XAS) is a widely used X-ray diagnostic method. While synchrotrons have large communities of XAS users, its use on X-Ray Free Electron Lasers (XFEL) facilities has been rather limited. At a first glance, the…

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…

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 Gamma-ray Large Area Space Telescope (GLAST) is a next generation high energy gamma-ray observatory due for launch in Fall 2007. The primary instrument is the Large Area Telescope (LAT), which will measure gamma-ray flux and spectra…

Laser-driven compact particle accelerators can provide ultrashort pulses of broadband X-rays, well suited for undertaking X-ray absorption spectroscopy measurements on a femtosecond timescale. Here the Extended X-ray Absorption Fine…

We report on the results of a search for CO(3-2) emission from the galaxy counterpart of a high-metallicity Damped Ly-alpha Absorber (DLA) at z=2.5832 towards the quasar Q0918+1636. We do not detect CO emission from the previously…

GRB absorption spectroscopy opened up a new window in the study of the high redshift Universe, especially with the launch of the Swift satellite and the quick and precise localization of the afterglow. Eight-meter class telescopes can be…

Measurements of element abundances in damped Lyman alpha systems are providing new means to investigate the chemical evolution of galaxies, particularly at early times. We review progress in this area, concentrating on recent efforts to…

Gas surrounding high redshift galaxies has been studied through observations of absorption line systems toward background quasars for decades. However, it has proven difficult to identify and characterize the galaxies associated with these…

We present intermediate resolution ($\sim3$ \AA ) spectra of the Ly$\alpha$ emission from 15 high redshift radio galaxies ($z>2$). Together with previously published spectra we analyze data for a sample of 18 objects. In 11 of the 18 radio…