Related papers: HUT Observations of the Lyman Limit in AGN: Implic…

We observed the Seyfert 1 galaxy NGC 3516 twice during the flight of Astro-2 using the Hopkins Ultraviolet Telescope in March 1995. Simultaneous X-ray observations were performed with ASCA. Our far-ultraviolet spectra cover the spectral…

We present the results of ultraviolet spectral monitoring of the Seyfert galaxy NGC 4151 performed by the Hopkins Ultraviolet Telescope during the Astro-2 mission. We show how the response of the Lyman continuum optical depth to variations…

We have reevaluated the constraints on the Lyman continuum emission from four starburst galaxies observed with the Hopkins Ultraviolet Telescope (HUT) during the Astro-2 mission. Applying a detailed model of the absorption by interstellar…

The ionizing fluxes from quasars and other active galactic nuclei (AGN) are critical for interpreting their emission-line spectra and for photoionizing and heating the intergalactic medium (IGM). Using far-ultraviolet spectra from the…

The rest-frame ultraviolet (UV) spectra of active galactic nuclei (AGNs) are important diagnostics of both accretion disk physics and their contribution to the metagalactic ionizing UV background. Though the mean AGN spectrum is well…

We present an ultraviolet spectroscopic survey of strong H I absorbers in the intergalactic medium, probing their evolution over the last 6-7 Gyr at redshifts $0.24 \leq z \leq 0.84$. We measure column densities $N_{\rm HI} \,( {\rm…

We present new results for a sample of 33 narrow-lined UV-selected active galactic nuclei (AGNs), identified in the course of a spectroscopic survey for star-forming galaxies at z ~ 2-3. The rest-frame UV composite spectrum for our AGN…

The extraordinarily bright quasar PHL 1811 at a redshift z = 0.192 provides an attractive opportunity to use ultraviolet absorption-line spectroscopy to study the properties of gas systems in the local universe. An R = 20,000 far-UV…

The ionizing fluxes from quasars and other active galactic nuclei (AGN) are critical for interpreting the emission-line spectra of AGN and for photoionization and heating of the intergalactic medium. Using ultraviolet spectra from the…

We present a detailed analysis of the most luminous and obscured Active Galactic Nuclei (AGNs) detected in the ultra-hard X-ray band (14-195 keV) by Swift/BAT. Our sample comprises 21 X-ray luminous (log $L_X/{\rm erg\,s^{-1}}>44.6$, 2-10…

As part of a large spectroscopic survey of z>5 Lyman break galaxies (LBGs), we have identified a single source which is clearly hosting an AGN. Out of a sample of more than fifty spectroscopically-confirmed R-band dropout galaxies at z~5…

We created a sample of nearby QSOs selected from the Hamburg/ESO survey and the Veron-Cetty & Veron catalog, with a limiting redshift of z<0.06, which consists of 63 objects. In this contribution, we present the results of our ISAAC Ks-band…

We present a survey for optically thick Lyman limit absorbers at z<2.6 using archival Hubble Space Telescope observations with the Faint Object Spectrograph and Space Telescope Imaging Spectrograph. We identify 206 Lyman limit systems…

We present a sample of twenty-one ROSAT bright active galactic nuclei (AGN), representing a range of spectral classes, and selected for follow-up snap-shot observations with XMM-Newton. The typical exposure was between 5-10 ks. The objects…

The gas added and removed from galaxies over cosmic time greatly affects their stellar populations and star formation rates. QSO absorption studies in close QSO/galaxy pairs create a unique opportunity to study the physical conditions and…

From UV spectra of the bright quasar PHL 1811 recorded by FUSE and the E140M configuration on STIS, we have determined the abundances of various atomic species in a Lyman limit system at z = 0.0809 with log N(H I) = 17.98. Considerably more…

Using the Far Ultraviolet Spectroscopic Explorer (FUSE) we have obtained 87 spectra of 57 low-redshift (z<0.15) active galactic nuclei (AGN). This sample comprises 53 Type 1 AGN and 4 Type 2. All the Type 1 objects show broad O VI 1034…

We present a multi wavelength analysis of 28 of the most luminous low-redshift narrow-line, ultra-hard X-ray selected active galactic nuclei (AGN) drawn from the 70 month Swift/BAT all-sky survey, with bolometric luminosities of…

We report on HST/STIS spectra of the Lyman-alpha emission in the central dominant galaxies in three rich clusters of galaxies. We find evidence for a population of clouds in the intracluster medium.We detect 10 Ly-alpha absorption systems…

We present cosmological-scale 3-dimensional (3D) neutral hydrogen ({\sc Hi}) tomographic maps at $z=2-3$ over a total of 837 deg$^2$ in two blank fields that are developed with Ly$\alpha$ forest absorptions of 14,736 background Sloan…