Luminous arcs: An observational update

Abstract

This presentation will give an up-date of the observations that have been carried out by the main investigators of an international effort to survey gravitational arcs. But in order not to duplicate the review given only few months ago at Cambridge by G. Soucail (1991) we will mainly emphasize some of the most recent results obtained within the framework of the ESO-CFHT key program: last discoveries of new large arcs, determination of the distance of the background population of faint galaxies forming the gravitational arclets and what the observations have already revealed about distribution of dark matter within the center of rich clusters of galaxies. All these topics are in rapid progress from the observational point of view and many new observational results are not yet published. Therefore, this presentation will undoubtedly be biased toward the Toulouse survey. Furthermore, some exciting new advances on the spectroscopy of arcs or on the IR survey of the Durham group to study the evolution of distant galaxies will be also occulted or just mentioned since most of them have not been officially released. The use of the arc(let)s to derive cosmological parameters will not be discussed. It is up to now too speculative considering the state of the art for the observations.