We have compiled a new and extensive catalog of heavy-element QSO absorption line systems and analyzed the distribution of absorbers in bright and faint QSOs, to search for gravitational lensing of background QSOs by the matter associated with the absorbers. There is a highly significant excess of C iv absorbers in bright QSOs in the redshift range z = 1.2 − 3.2, and this excess increases stron...

We report on a survey for narrow (FWHM < 600 km s) C iv absorption lines in a sample of bright quasars at redshifts 1.8 6 z < 2.25 in the Sloan Digital Sky Survey. Our main goal is to understand the relationship of narrow C iv absorbers to quasar outflows and, more generally, to quasar environments. We determine velocity zeropoints using the broad Mg ii emission line, and then measure the absor...

Absorption line studies of galaxies along the line-of-sight to distant quasars allow a direct observational link between the properties of the extended gaseous disk/halo and of the star forming region of galaxies. In these proceedings we review recent work on Ca ii absorbers detected in the SDSS at 0.4 < z < 1.3 which, because of their dust content and chemical properties, may lie spatially clo...

With close pairs of quasars at different redshifts, a background quasar sightline can be used to study a foreground quasar’s environment in absorption. We used a sample of 17 Lyman limit systems with column density NHI > 10 19 cm selected from 149 projected quasar pair sightlines, to investigate the clustering pattern of optically thick absorbers around luminous quasars at z ∼ 2.5. Specifically...

We present results from a survey of weak Mg ii absorbers in the VLT/UVES spectra of 81 QSOs obtained from the ESO archive. In this survey, we identified 112 weak Mg ii systems within the redshift interval 0.4 < z < 2.4 with 86 % completeness down to a rest-frame equivalent width of Wr(2796) = 0.02 Å, covering a cumulative redshift path length of ∆Z ∼ 77.3. From this sample, we estimate that the...

Observations at intermediate redshifts reveal the presence of numerous compact, weak Mg ii absorbers with near to supersolar metallicities, often surrounded by extended regions that produce C iv and/or O vi absorption, in circumgalactic medium large impact parameters from luminous galaxies. Their origin and nature remain unclear. We hypothesize undetected satellite dwarf galaxies are responsibl...

Paul Alivisatos Professor of Chemistry and Materials Science University of California, Berkeley There are numerous situations in which a light weight composite with high energy absorbing capabilities can be of use in the Air Force mission, for protection against impact of projectiles or laser beams. Advances in nanoscience have created a new opportunity to design such composites, as it is now p...

Strong foreground absorption features from singly ionized magnesium (Mg II) are commonly observed in the spectra of quasars and are presumed to probe a wide range of galactic environments. To date, measurements of the average dark matter (DM) halo masses of intervening Mg II absorbers by way of large-scale cross-correlations with luminous galaxies have been limited to z < 0.7. In this work, we ...

Recent ultraviolet and X-ray observations of intergalactic OVI and OVII absorption systems along lines of sight to bright quasars have opened a new window onto the “warm-hot intergalactic medium” (WHIM). These systems appear to provide a significant reservoir for baryons in the local universe, and comparison to cosmological simulations suggests that their abundance roughly matches theoretical p...