Related papers: Quasar-galaxy associations
We have used spectra of 181 projected quasar pairs at separations $\le 1.5$ arcmins from the Sloan Digital Sky-Survey Data Release 12 in the redshift range of 2.5 to 3.5 to probe the proximity regions of the foreground quasars. We study the…
At the faint end of the deepest X-ray surveys, a population of X-ray luminous galaxies is seen. In this paper, we present the results of a cross-correlation between the residual, unresolved X-ray photons in a very deep X-ray survey and the…
We present a first attempt to reveal the possible existence of large foreground mass condensations directly responsible for the gravitational magnification of four distant luminous radiosources and one optical QSO. The technique uses a weak…
Weak gravitational lensing of distant galaxies by foreground structures has proven to be a powerful tool to study the mass distribution in the universe. Nowadays, attention has shifted from clusters of galaxies to the statistical properties…
We simulated both the matter and light (galaxy) distributions in a wedge of the universe and calculated the gravitational lensing magnification caused by the mass along the line of sight of galaxies and galaxy groups identified in sky…
We compile a sample of 38 galaxy clusters which have both X-ray and strong lensing observations, and study for each cluster the projected offset between the dominant component of baryonic matter center (measured by X-rays) and the…
A search for emission lines in foreground galaxies in quasar spectra (z(gal) < z(QSO)) of the Sloan Digital Sky Survey (SDSS) data release 5 (DR5) reveals 23 examples of quasars shining through low redshift, foreground galaxies at small…
Deep optical images have been gathered for a nearly complete sample of radio galaxies from the Revised 3rd Cambridge (3CR) Catalog in the redshift range 0.15 < z < 0.65. Total and nuclear magnitudes and colors have been extracted. 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…
The most heavily-obscured, luminous quasars might represent a specific phase of the evolution of actively accreting supermassive black holes and their host galaxies, possibly related to mergers. We investigated a sample of the most luminous…
Quasars are the most luminous sources in the Universe. They are currently observed out to redshift z ~ 7 when the Universe was less than one tenth of its present age. Since their discovery 50 years ago astronomers have dreamed of using them…
We use the large catalogues of haloes available for the Millennium Simulation to test whether recently merged haloes exhibit stronger large-scale clustering than other haloes of the same mass. This effect could help to understand the very…
D. Reimers and H.-J. Hagen report in A&A 329, L25 (1998) that a QSO of z = .807 is a "by chance projection" on the center of a galaxy of z = .009. A considerable amount of previously published evidence would lead us to expect an active, low…
Based on a cross-correlation analysis of X-ray selected QSOs with faint (B<20.5) galaxies, we find a 5sigma galaxy excess around low-redshift (z<0.3) QSOs with an amplitude identical to that of the galaxy angular correlation function. The…
A significant cross-correlation between the unresolved X-ray background (XRB) at soft energies (0.5 to 2 keV) and foreground bright galaxies has now been reported in several studies. This cross-correlation has been interpreted in terms of a…
Quasars, powered by gas accretion onto supermassive black holes, rank among the most energetic objects of the Universe. While they are thought to be ignited by galaxy mergers and affect the surrounding gas, observational constraints on both…
Le Brun et al. (1997) presented the first identifications of the galaxies giving rise to 7 intermediate redshift damped Ly-alpha (DLA) absorption systems. Here, we study the gravitational lensing properties of these foreground galaxies…
We have detected the host galaxies of 16 nearby, radio-quiet quasars using images obtained with the Near-Infrared Camera and Multi-Object Spectrometer (NICMOS). We confirm that these luminous quasars tend to live in luminous, early-type…
A galaxy can act as a gravitational lens, producing multiple images of a background object. Theory predicts there should be an odd number of images but, paradoxically, almost all observed lenses have 2 or 4 images. The missing image should…
We present a cross-correlation analysis to constrain the faint galaxy contribution to the cosmic X-ray background (XRB). Cross-correlating faint optical galaxy catalogues with unidentified X-ray sources from 3 deep ROSAT fields we find that…