The JVAS/Class Gravitational Lens Surveys
The JVAS/CLASS surveys are designed to find gravitational lens systems in which the flat spectrum cores of radio sources are multiply imaged. The prime motivation for the searches is to find systems from which the Hubble constant can be determined by measuring time delays and to produce statistically clean samples of lenses which can be used for cosmological investigations. Up to now some 8000 flat spectrum sources have been mapped with the VLA with a resolution of 200 mas. When complete we hope to have surveyed 10,000 sources. High resolution MERLIN and VLBA follow-up of the candidates is still in progress. To date 11 lens systems have been discovered. Time delays have been measured for 2 of these systems. HST and other observations almost always show a lensing galaxy so there is no evidence for "dark lenses". The maximum image separations peak between 1 and 2 arcsec.