EDP Sciences
Free access
Volume 414, Number 2, February I 2004
Page(s) 425 - 428
Section Extragalactic astronomy
DOI http://dx.doi.org/10.1051/0004-6361:20034184

A&A 414, 425-428 (2004)
DOI: 10.1051/0004-6361:20034184

Time-delay quasars: Scales and orders of magnitudes

P. 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 $\sim 10^{-11}$, 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

SIMBAD Objects

© ESO 2004