A&A 414, 425-428 (2004)
Time-delay quasars: Scales and orders of magnitudesP. Saha
Astronomy Unit, Queen Mary and Westfield College, University of London, London E1 4NS, UK Observatoire astronomique, 11 rue de l'Université, 67000 Strasbourg, France
(Received 12 August 2003 / Accepted 18 September 2003)
We can think of a lensed quasar as taking the Hubble time, shrinking it by , and then presenting the result to us as a time delay; the shrinking factor is of the order of fractional sky-area that the lens occupies. This cute fact is a straightforward consequence of lensing theory, and enables a simple rescaling of time delays. Observed time delays have a 40-fold range, but after rescaling the range reduces to 5-fold. The latter range depends on details of the lens and lensing configuration - for example, quads have systematically shorter rescaled time delays than doubles - and is as expected from a simple model. The hypothesis that observed time-delay lenses all come from a generalized-isothermal family can be ruled out. But there is no indication of drastically different populations either.
Key words: Gravitational lensing -- galaxies: quasars: general
© ESO 2004