Light on dark lenses

We present an update of the status of the Cosmic Lens All-Sky Survey (CLASS). Twelve lenses have been found to date in CLASS together with the earlier Jodrell Bank-VLA Astrometric Survey (JVAS). Six other sources are under investigation as possible lenses. To date, all lens systems studied optically have been shown to have associated lensing galaxies to a limiting I magnitude of 23-24. These observations place severe constraints on published claims that dark ( M/L > 100 ) galaxies form a significant fraction of the general population of galaxies.TMR Program, Research Contract ERBFMRXCT960034 'CERES