The new two-image gravitational lens system class B2319+051

We report the discovery of a new two-image gravitational lens system, CLASS B2319+051, from the Cosmic Lens All-Sky Survey. Radio imaging with the Ver y Large Array (VLA) and Multielement Radio-linked Interferometer Network (M ERLIN) shows two compact components with a flux density ratio of similar or equal to5:1, separated by 1."36. Observations with the Very Long Baseline Array (VLBA) resolve each of the radio components into a pair of parity-rev ersed subcomponents. Hubble Space Telescope observations with the Near-Infr ared Camera and Multi-Object Spectrometer (NICMOS) show a bright elliptical galaxy (G1) coincident with the radio position, and a second irregular gal axy (G2) 3."4 to the northwest. Previous spectroscopic studies have indicat ed that these galaxies are at different redshifts (z(G1) = 0.624, z(G2) = 0 .588). Infrared counterparts to the lensed radio components are not detecte d in the NICMOS image, and the source redshift has not yet been determined. Preliminary mass modeling based on the VLBA subcomponent data indicates th at the lensing potential includes a strong external shear contribution. A V LA monitoring program is currently being undertaken to measure the differen tial time delay.