Related papers: The Origins of a Rich Absorption Line Complex in a…
Detailed Monte Carlo Inversion analysis of the spectral lines from three Lyman limit systems (LLS) [N(HI) > 10^{17} cm^-2] and nine lower N(HI) systems [2 10^{14} < N(HI) < 2 10^{16} cm^-2] observed in the VLT/UVES spectra of Q0347-3819 (in…
We report the discovery of disappearance of Mg ii, Al iii, C iv, and Si iv broad absorption lines (BALs) at the same velocity, accompanied by a new Civ BAL emerging at a higher velocity, in the quasar J0827+4252 at z = 2.038. This is the…
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…
The most robust way for determining the distance of quasar absorption outflows is the use of troughs from ionic excited states. The column density ratio between the excited and resonance states yields the outflow number density. Combined…
We assemble 207 variable quasars from the Sloan Digital Sky Survey, all with at least 3 observations, to analyze C IV narrow absorption doublets, and obtain 328 C IV narrow absorption line systems. We find that 19 out of 328 C IV narrow…
We present an analysis of the complex associated system of the high-redshift QSO HE2347-4342. Absorption features of HI, CIII, CIV, NV, and OVI with up to 16 components occur in the optical spectral range located up to 1500 km/s redwards…
We present a detailed analysis of three metal absorption systems observed in the spectrum of the HDF-South quasar J2233-606 (z_em = 2.238), taking advantage of new VLT-UVES high resolution data (R=45000, S/N = 40-60, \lambda\lambda…
We investigate the NV absorption signal along the line of sight of background quasars, in order to test the robustness of the use of this ion as criterion to select intrinsic (i.e. physically related to the quasar host galaxy) narrow…
We analyze absorption troughs from two outflows within PKS J0352-0711 (S1 at $-$1950 km s$^{-1}$ and S2 at $-$3150 km s$^{-1}$) from spectra taken with Hubble Space Telescope/Cosmic Origin Spectrograph, which cover the diagnostic-rich…
We detect the 21 cm line of neutral hydrogen in absorption at a redshift of 0.673 towards the 1 Jy radio source 1504+377. The 1504+377 radio source is located toward the center of what appears to be an inclined disk galaxy at z = 0.674. The…
We examine the kinematics of the gas in the environments of galaxies hosting quasars at $z\sim2$. We employ 148 projected quasar pairs to study the circumgalactic gas of the foreground quasars in absorption. The sample selects foreground…
CRTS J084133.15+200525.8 is an optically bright quasar at z=2.345 that has shown extreme spectral variability over the past decade. Photometrically, the source had a visual magnitude of V~17.3 between 2002 and 2008. Then, over the following…
We present HST/COS observations of highly ionized absorption lines associated with a radio-loud QSO at $z=1.1319$. The absorption system has multiple velocity components, tracing gas that is largely outflowing from the QSO at velocities of…
We report the detection of a third HI 21-cm absorber in the sight-line towards the z=2.64 quasar MG J0414+0534 (4C +05.19). In addition to the absorption at the host redshift and in the z=0.96 gravitational lens, we find, through a…
We have obtained high, 11 and 14 \kms, and medium, 40 and 53 \kms, resolution spectra of the $z_{em} = 4.11$ quasar Q0000--2619 covering the range 4400 \AA\ to 9265 \AA . We identify nine metal absorption systems, of which four were…
We have discovered a third quasar absorption system which is consistent with a low deuterium to hydrogen abundance ratio, D/H = 3.4 times 10^-5. The z ~ 2.8 partial Lyman limit system towards QSO 0130-4021 provides the strongest evidence to…
We present initial results from the first systematic survey for MgII quasar absorption lines at z > 2.5. Using infrared spectra of 46 high-redshift quasars, we discovered 111 MgII systems over a path covering 1.9 < z < 6.3. Five systems…
Quasar outflows often consist of two clouds with velocity separations matching the doublet spacings of common UV resonance transitions, a phenomenon known as line-locking, which is commonly observed in quasar spectra. Multiple clouds can be…
We have searched for redshifted absorption in the 21 cm line of neutral hydrogen toward `red quasars', which are extragalactic radio sources with a steep spectral drop between optical and infrared wavelengths. The success rate for detecting…
A fraction of quasars present broad absorption lines, produced by outflowing gas with typical velocities of 3000 - 10,000 km/s. If the outflowing gas fills a significant fraction of the volume where it resides, then it will be highly…