May 5, 2005
We report the discovery of a new gravitational lens system from the CLASS survey, CLASS B0631+519. VLA, MERLIN and VLBA observations show a doubly-imaged radio core, a doubly-imaged lobe and a second lobe that is probably quadruply-imaged. The maximum image separation is 1.16 arcseconds. The VLBA resolves the most magnified image of the flat-spectrum radio core into a number of sub-components spread across approximately 20 milli-arcseconds. Optical and near-infrared imaging with the ACS and NICMOS cameras on the HST show that there are two galaxies along the line of sight to the lensed source, as was previously discovered by optical spectroscopy. The nearer galaxy at z=0.0896 is a small blue irregular, while the more distant galaxy at z=0.6196 is an elliptical type and appears to contribute most of the lensing effect. The host galaxy of the lensed source is visible in NICMOS imaging as a set of arcs that form an almost complete Einstein ring. Mass modelling using non-parametric techniques can reproduce the ring and indicates that the irregular galaxy has a (localised) effect on the flux density distribution in the Einstein ring at the 5-10% level.
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April 25, 2001
We report the discovery of a new two-image gravitational lens system from the Cosmic Lens All-Sky Survey, CLASS B2319+051. Radio imaging with the Very Large Array (VLA) and Multi-Element Radio-Linked Interferometer Network (MERLIN) shows two compact components with a flux density ratio of 5:1, separated by 1.36 arcsec. Observations with the Very Long Baseline Array (VLBA) resolve each of the radio components into a pair of parity-reversed subcomponents. Hubble Space Telescope...
October 22, 2004
We present observations of CLASS B2108+213, the widest separation gravitational lens system discovered by the Cosmic Lens All-Sky Survey. Radio imaging using the VLA at 8.46 GHz and MERLIN at 5 GHz shows two compact components separated by 4.56 arcsec with a faint third component in between which we believe is emission from a lensing galaxy. 5-GHz VLBA observations reveal milliarcsecond-scale structure in the two lensed images that is consistent with gravitational lensing. Op...
November 10, 1998
We have discovered a new gravitational lens in the Cosmic Lens All-Sky Survey (CLASS). B2045+265 is a four-image system with a maximum separation of 1.9 arcsec. A fifth radio component is detected, but its radio spectrum and its positional coincidence with infrared emission from the lensing galaxy strongly suggests that it is the radio core of the lensing galaxy. This implies that the B2045+265 system consists of a flat-spectrum radio source being lensed by another flat-spect...
August 2, 2000
We present the discovery of CLASS B0739+366, a new gravitational lens system from the Cosmic Lens All-Sky Survey. Radio imaging of the source with the Very Large Array (VLA) shows two compact components separated by $0\farcs54$, with a flux density ratio of $\sim$ 6:1. High-resolution follow-up observations using the Very Long Baseline Array (VLBA) at 1.7 GHz detect weak, parity-reversed jet emission from each of the radio components. Hubble Space Telescope NICMOS F160W obser...
October 31, 1997
We report the discovery of the most complex arcsec-scale radio gravitational lens system yet known. B1933+503 was found during the course of the CLASS survey and MERLIN and VLA radio maps reveal up to 10 components. Four of these are compact and have flat spectra; the rest are more extended and have steep spectra. The background lensed object appears to consist of a flat spectrum core (quadruply imaged) and two compact "lobes" symmetrically disposed relative to the core. One ...
October 23, 2002
We report the discovery of a new gravitational lens system from the CLASS survey. Radio observations with the VLA, the WSRT and MERLIN show that the radio source B0850+054 is comprised of two compact components with identical spectra, a separation of 0.7 arcsec and a flux density ratio of 6:1. VLBA observations at 5 GHz reveal structures that are consistent with the gravitational lens hypothesis. The brighter of the two images is resolved into a linear string of at least six ...
November 26, 1998
We present the discovery of a new gravitational lens system with two compact radio images separated by 0.701+-0.001 arcsec. The lens system was discovered in the Cosmic Lens All Sky Survey (CLASS) as a flat spectrum radio source. Both radio components show structure in a VLBA 8.4 GHz radio image. No further extended structure is seen in either the VLA, MERLIN or VLBA images. Hubble Space Telescope (HST) WFPC2 images in F555W and F814W show two extended objects close to the ra...
December 7, 2007
The gravitational lens system CLASS B2108+213 has two lensed images separated by 4.56 arcsec. Such a wide image separation suggests that the lens is either a massive galaxy, or is composed of a group of galaxies. To investigate the structure of the lensing potential we have carried out new high resolution imaging of the two lensed images at 1.7 GHz with the VLBA and at 5 GHz with global VLBI. Compact and extended emission is detected from the two lensed images, which provides...
November 28, 2000
HST V and I-band observations show that the gravitational lens B1359+154 consists of six images of a single z_s=3.235 radio source and its star-forming host galaxy, produced by a compact group of galaxies at z_l = 1. VLBA observations at 1.7 GHz strongly support this conclusion, showing six compact cores with similar low-frequency radio spectra. B1359+154 is the first example of galaxy-scale gravitational lensing in which more than four images are observed of the same backgro...
February 5, 2004
We present new observations of the gravitational lens system CLASS B0128+437. HST observations detect a very faint, extended object in I-band with no emission from the lensed images visible; no detection at all is made in V-band. The lens system is detected with much higher signal to noise with UKIRT in K-band, but the resolution is not sufficient to allow the lensed images and the lens galaxy to be separated. A careful astrometric calibration, however, suggests that the peak...