We analyze the available sample of double quasars, and investigate their physical properties. Our sample comprises 85 pairs, selected from the Sloan Digital Sky Survey (SDSS). We derive physical parameters for the engine and the host, and model the dynamical evolution of the pair. First, we compare different scaling relationships between massive black holes and their hosts (bulge mass, velocity...

We use simple comparisons of the optical and radio properties of the wide separation (3 < < 10) quasar pairs to demonstrate that they are binary quasars rather than gravitational lenses. The most likely model is that all the pairs are binary quasars, with a one-sided 2{ (1{ ) upper limit of 22% (8%) on the lens fraction. Simple models for the expected enhancement of quasar activity during galax...

Numerical simulations and theoretical studies of the gravitational microlensing effect of a population of small bodies distributed along the line of sight to a compact light source such as a quasar indicate that caustic crossing effects will be present given a sufficiently large optical depth to lensing. These events will produce characteristic patterns in the quasar light curve. In this paper ...

From examination of only 4 deg of sky in the NOAO Deep Wide-Field Survey (NDWFS) region, we have identified the first radio-loud quasar at a redshift z > 6. The object, FIRST J1427385+331241, was discovered by matching the FLAMEX IR survey to FIRST survey radio sources with NDWFS counterparts. One candidate z > 6 quasar was found, and spectroscopy with the Keck II telescope confirmed its identi...

The study of molecular gas in quasar host galaxies addresses a number of interesting questions pertaining to the hosts' ISM, to unified schemes relating quasars and IR galaxies, and to the processes fueling nuclear activity. In this contribution I review observations of molecular gas in quasar hosts from z = 0.06 to z = 4.7. The Cloverleaf quasar at z = 2.5 is featured as a case where there are...

During the course of Hamburg/CfA Bright Quasar Survey we discovered a bright (B = 15.9), high redshift (z em = 2.51) quasar HS 1603+3820. The quasar has a rich complex of Civ absorbers, containing at least five systems, all within 3000 km s −1 from one another. Despite large ejection velocity (v ej > 5000 km s −1 for all components) the complex is likely to be associated with the quasar. There ...

In the gravitational lens system Q2237+0305 the cruciform quasar image geometry is twisted by ten degrees by the lens effect of a bar in the lensing galaxy. This effect can be used to measure the mass of the bar. We construct a new lensing model for this system with a power-law elliptical bulge and a Ferrers bar. The observed ellipticity of the optical isophotes of the galaxy leads to a nearly ...

We present midand far-IR photometry of the high-redshift (z=4.69) dusty quasar BR1202-0725. The quasar was detected in the near-IR, at a flux level (0.7±0.2 mJy) consistent with an average Radio-Quiet Quasar at it’s redshift. Only upper limits for the emission were obtained in the far-IR. These upper limits, when combined with data from ground-based telescopes, are the first direct evidence for...

The monitoring of the gravitational lens Q2237+0305 carried out by the OGLE group during 1997–1999 is analyzed. The significant light amplifications in the C and A quasar components with maxima in mid-and late 1999, respectively, are interpreted as the crossing of microlens caustics by the source. A constraint on the emitting-region size R ≤ 10 15 cm has been obtained from the light-curve shape...

Preliminary results are described for emission-line imaging of the field of a quasar at z = 0.9 with a unique new instrument — the TAURUS Tunable Filter (TTF). At least fourteen [O ii]-emitting galaxy candidates are found within ±750km s of the quasar redshift with a significance of > 3σ. Another eight candidates (> 3σ) are also found with relative velocities ±750−1500km s from the quasar, indi...