Light on dark lenses

N. Jackson, Phillip Helbig: I. W. A. Browne & L. V. E. Koopmans

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&emdash;24. These observations place severe constraints on published claims that dark galaxies (more than one trillion solar masses but with normal luminosity) form a significant fraction of the general population of galaxies.