Related papers: A Simple Disk Wind Model for Broad Absorption Line…
New near- and far-ultraviolet (NUV and FUV) HST spectra of Mrk 231, the nearest quasar known, are combined with ground-based optical spectra to study the remarkable dichotomy between the FUV and NUV-optical spectral regions in this object.…
We are involved in a program to derive properties of broad absorption line (BAL) winds in quasars using combined UV and X-ray observations. A major obstacle is large uncertainties in the derived BAL column densities because of partial…
Hyper-luminous Quasi-Stellar Objects (QSOs) represent the ideal laboratory to investigate Active Galactic Nuclei (AGN) feedback mechanism since their formidable energy release causes powerful winds at all scales and thus the maximum…
The ultraviolet (UV) bright accretion disc in active galactic nuclei (AGN) should give rise to line driving, producing a powerful wind which may play an important role in AGN feedback as well as in producing structures like the broad line…
Aims. The co-evolution of galaxies and super massive black holes (SMBHs) requires that some sort of feedback mechanism is operating during the active galactic nuclei (AGN) phases. AGN driven winds are the most likely candidates for such…
We present high spectral resolution VLT observations of the BAL quasar SDSS J0318-0600. This high quality data set allows us to extract accurate ionic column densities and determine an electron number density of n_e=10^3.3 +/- 0.2 cm^-3 for…
The origin, geometry and kinematics of the broad line region (BLR) gas in quasars and active galactic nuclei (AGN) are uncertain. We demonstrate that clumpy biconical disc winds illuminated by an AGN continuum can produce BLR-like spectra.…
Broad absorption line (BAL) quasars probe the high velocity gas ejected by luminous accreting black holes. BAL variability timescales place constraints on the size, location, and dynamics of the emitting and absorbing gas near the…
Background quasars are potentially sensitive probes of galactic outflows provided that one can determine the origin of the absorbing material since both gaseous disks and strong bipolar outflows can contribute to the absorption…
Several works have studied the relation between X-ray, UV, and wind properties in broad absorption line quasars (BALQSOs), generally concluding that the formation of strong winds is tightly connected with the suppression of the ionizing…
Past X-ray observations of the nearby luminous quasar PDS 456 (at $z=0.184$) have revealed a wide angle accretion disk wind (Nardini et al. 2015), with an outflow velocity of $\sim-0.25c$, as observed through observations of its…
We analyze archived Chandra and XMM-Newton X-ray observations of 536 Sloan Digital Sky Survey (SDSS) Data Release 5 (DR5) quasars (QSOs) at 1.7 <= z <= 2.7 in order to characterize the relative UV and X-ray spectral properties of QSOs that…
It is been known for more than a decade that BALQSOs (broad absorption line quasars) are highly attenuated in the X-ray regime compared to other quasars, especially in the soft band ($< $ 1 keV). Using X-ray selection techniques we have…
A quasar wind model is proposed to describe the spatial and velocity structure of the broad line region. This model requires detailed photoionization and magnetohydrodynamic simulation, as the broad line region it too small for direct…
We search for velocity changes (i.e., acceleration/deceleration) of narrow absorption lines (NALs) that are intrinsic to the quasars, using spectra of 6 bright quasars that have been observed more than once with 8-10m class telescopes.…
We recently presented radio observations of a large sample of radio-loud broad absorption line (BAL) quasars from the SDSS and FIRST surveys, as well as a well matched sample of unabsorbed quasars, primarily to measure their radio spectral…
We present X-shooter at the Vewry Large Telescope observations of a sample of 10 luminous, X-ray obscured QSOs at z$\sim1.5$ from the XMM-COSMOS survey, expected to be caught in the transitioning phase from starburst to active galactic…
Using 190,000 spectra from the seventeenth data release of the Sloan Digital Sky Survey, we investigate the ultraviolet emission line properties in z=2 quasars. Specifically, we quantify how the shape of CIV 1549A and the equivalent width…
Broad Absorption Lines indicate gas outflows with velocities from thousands km/s to about 0.2 the speed of light, which may be present in all quasars and may play a major role in the evolution of the host galaxy. The variability of…
We present the first large sample of absorption systems in paired QSOs consisting of 691 absorption systems in the spectra of 310 QSOs including 170 pairings. All these absorption systems have metal lines, usually C IV or Mg II. We see 17…