Related papers: CLASS B0739+366: A new two-image gravitational len…

Previous observations of the environments of the lensing galaxies in gravitational lens systems suggest that many of the lensing galaxies are associated with small groups of galaxies. As a result, we have begun a coordinated program to…

We present spectra of three gravitational lens systems taken with the Low Resolution Imaging Spectrograph on the W. M. Keck Telescopes. All of the systems were discovered in the JVAS and CLASS radio surveys, which were designed to find…

We present Hubble Space Telescope (HST) infrared images of four gravitational lens systems from the JVAS/CLASS gravitational lens survey and compare the new infrared HST pictures with previously published WFPC2 HST optical images and radio…

The four-component gravitational lens CLASS B1608+656 has been monitored with the VLA for two seasons in order to search for time delays between the components. These time delays can be combined with mass models of the lens system to yield…

We present a series of high resolution radio and optical observations of the CLASS gravitational lens system B1152+199 obtained with the Multi-Element Radio-Linked Interferometer Network (MERLIN), Very Long Baseline Array (VLBA) and Hubble…

We report the discovery of a new double-image gravitational lens resulting from our search for lenses in the southern sky. Radio source PMN J2004-1349 is composed of two compact components separated by 1.13 arcseconds in VLA, MERLIN and…

We report the discovery of a new low-redshift galaxy-scale gravitational lens, identified from a systematic search of publicly available MUSE observations. The lens galaxy, 2MASXJ04035024-0239275, is a giant elliptical at $z$ = 0.06604 with…

The Hubble constant value is currently known to 10% accuracy unless assumptions are made for the cosmology (Sandage et al. 2006). Gravitational lens systems provide another probe of the Hubble constant using time delay measurements.…

Aims: We measure the redshift of the lensing galaxy in eight gravitationally lensed quasars in view of determining the Hubble parameter H_0 from the time delay method. Methods: Deep VLT/FORS1 spectra of lensed quasars are spatially…

We report on the results of a spectroscopic survey of the environments of the gravitational lens systems CLASS B1600+434 (z_l = 0.41, z_s = 1.59) and CLASS B2319+051 (z_l = 0.62). The B1600+434 system has a time delay measured for it, and…

We present a novel pilot search for gravitational lenses in the mJIVE-20 survey, which observed $24\,903$ radio sources selected from FIRST with the VLBA at an angular resolution of 5 mas. We have taken the visibility data for an initial…

We present a refined gravitational lens model of the four-image lens system B1608+656 based on new and improved observational constraints: (i) the three independent time-delays and flux-ratios from VLA observations, (ii) the radio-image…

The gravitational lens CLASS B1608+656 is the only four-image lens system for which all three independent time delays have been measured. This makes the system an excellent candidate for a high-quality determination of H_0 at cosmological…

Galaxies located in the environment or on the line of sight towards gravitational lenses can significantly affect lensing observables, and can lead to systematic errors on the measurement of $H_0$ from the time-delay technique. We present…

We present new results from a continuing Keck program to study gravitational lens systems. We have obtained redshifts for three lens systems, SBS 0909+532, HST 1411+5211, and CLASS B2319+051. For all of these systems, either the source or…

Galaxies and galaxy groups located along the line of sight towards gravitationally lensed quasars produce high-order perturbations of the gravitational potential at the lens position. When these perturbation are too large, they can induce a…

A gravitational lens model of the radio quasar B1422+231 is presented which can account for the image arrangement and approximately for the relative magnifications. The locations of the principal lensing mass and a more distant secondary…

We present a detailed strong lensing analysis of an HST/ACS legacy dataset for the first gravitational lens, Q0957+561. With deep imaging we identify 24 new strongly lensed features, which we use to constrain mass models. We model the…

We present HST observations of seven unusual objects from the HST ``snapshot survey'' of BL Lac objects, of which four are gravitational lens candidates. In three cases a double point sources is observed: 0033+595, with 1.58 arcsec…

We report the discovery of a new gravitational lens system. This object, ULAS J234311.93-005034.0, is the first to be selected by using the new UKIRT Infrared Deep Sky Survey (UKIDSS), together with the Sloan Digital Sky Survey (SDSS). The…