Related papers: The nature of NV absorbers at high redshift

We present a high signal-to-noise high resolution spectrum of the radio-quiet QSO HS1700+6416 (z = 2.72). Analysis of the absorption line systems with metals yields the following results. (1) The dense cluster of C IV doublets at 2.432 <…

A statistical study is presented of (a) the frequency of narrow CIV lambda 1549 absorption lines in 1.5 <~ z <~ 3.6 radio-quiet and radio-loud quasars, and of (b) the UV and radio properties of the absorbed quasars. The quasar sample is…

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 a moderate-resolution (~20 km/s) spectrum of the mini broad-absorption-line QSO PG1351+64 between 915-1180 A, obtained with the Far Ultraviolet Spectroscopic Explorer (FUSE). Additional spectra at longer wavelengths were also…

We statistically study the physical properties of a sample of narrow absorption line (NAL) systems looking for empirical evidences to distinguish between intrinsic and intervening NALs without taking into account any a priori definition or…

Using high resolution, high signal-to-noise ultraviolet spectra of the z = 0.9754 quasar PG1148+549 obtained with the Cosmic Origins Spectrograph (COS) on the Hubble Space Telescope, we study the physical conditions and abundances of…

We present a physically-based absorption-line model for the spectroscopic study of the intergalactic medium (IGM). This model adopts results from Cloudy simulations and theoretical calculations by Gnat and Sternberg (2007) to examine the…

Aim of this work is a broad-band study with INTEGRAL, Swift and XMM-Newton satellites of a sample of 9 blazars (7 FSRQ and 2 BL Lac) with redshift up to about 4. The spectral analysis has shown clear evidence of a flattening of the…

We have studied a sample of 415 associated (z_ab z_em; relative velocity with respect to QSO <3000km/s) Mg II absorption systems with 1.0<=z_ab<=1.86, in the spectra of SDSS DR3 QSOs, to determine the dust content and ionization state in…

We continue our recent work to characterize the plasma content of high-redshift damped and sub-damped Lyman-alpha systems (DLAs/sub-DLAs), which represent multi-phase gaseous (proto)galactic disks and halos seen toward a background source.…

We present a detailed analysis of chemical abundances in a sub-damped Lyman alpha absorber at z=1.839 towards the quasar B1101-26, based on a very-high-resolution (R ~ 75,000) and high-signal-to-noise (S/N >100) spectrum observed with the…

Recent FUSE and STIS observations of OVI absorption at low redshift along the sightline to distant quasars have been interpreted as the signature of a warm-hot diffuse component of the intergalactic medium (IGM). In these proceedings we…

We present the results of a large survey of HI, OVI, and CIII absorption lines in the low-redshift (z<0.3) intergalactic medium (IGM). We begin with 171 strong Lyalpha absorption lines (W>80 mA) in 31 AGN sight lines studied with the Hubble…

We list and analyze H I absorption lines at redshifts 2 < z < 4 with column density (12 < log(N_HI) < 19) in 40 high-resolutional (FWHM = 8.0 km/s) quasar spectra obtained with the Keck+HIRES. We de-blend and fit all H I lines within 1,000…

We present detailed photoionization models of well aligned optically thin C III absorption components at $2.1 < z < 3.4$. Using our models we estimate density ($n_{\rm \tiny H}$), metallicity ($[C/H]$), total hydrogen column density and…

We present a detailed analysis of the intergalactic metal-line absorption systems in the archival HST/STIS and FUSE ultraviolet spectra of the low-redshift quasar PKS1302-102 (z_QSO = 0.2784). We supplement the archive data with CLOUDY…

We present new UV spectra of the nucleus of the Seyfert 1 galaxy NGC 5548, which we obtained with the Space Telescope Imaging Spectrograph at high spectral resolution, in conjunction with simultaneous Chandra X-ray Observatory spectra.…

This paper provides a general reference for deriving the ionizations and metal abundances for absorption-line clouds in photoionization equilibrium with a QSO spectrum. The results include a quantitative assessment of the theoretical…

We estimate the He II to H I column density ratio, \eta = N(He II)/N(H I), in the intergalactic medium towards the high redshift (z_{em} = 2.885) bright quasar QSO HE 2347-4342 using Voigt-profile fitting of the H I transitions in the Lyman…

[Slightly Abridged] We present a detailed statistical analysis of the column densities, N, and Doppler parameters, b, of MgII absorbing clouds at redshifts 0.4<z<1.2. We use the HIRES/Keck data and Voigt profile (VP) fitting results…