AAS 207th Meeting, 8-12 January 2006
Session 200 Gravity: Lenses, Dark Matter and Waves
Oral, Thursday, 2:00-3:30pm, January 12, 2006, Ballroom/Salon 2

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[200.01] Higher-order Catastrophes in Gravitational Lenses

E. A. Baltz, R. D. Blandford, P. J. Marshall (KIPAC)

Future wide field sky surveys such as have been proposed by the SNAP and LSST teams will contain large numbers of gravitational lens systems. Such large samples afford the possibility of observing rare, exotic lens configurations in the form of higher order catastrophes. The fold (critical curve) and cusp catastrophes are well known; pairs of images are created for sources at these positions. Less well known are the swallowtail, butterfly and the umbilics. We have constructed a raytracing code that evaluates quantities which locally characterize these higher-order catastrophes. This necessarily goes beyond the usual deflection angle and magnification. Globally, catastrophes represent a change in the number of images or a change in the topology of the critical curves. We present a preliminary study of the detectability of lens systems exhibiting these features in large samples of lenses. Such systems depend sensitively on the source--lens configuration. It may be possible to find ``golden lenses'' which can be modeled much more accurately than is usually possible, giving insight into the shapes and density profiles of dark matter halos.

This work was supported by the U.S. Department of Energy under contract number DE-AC02-76SF00515.

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