Astronomy and Astrophysics – Astrophysics
Scientific paper
2005-07-05
Astron.Astrophys.447:419-430,2006
Astronomy and Astrophysics
Astrophysics
12 pages, 18 figures, accepted for publication on Astronomy and Astrophysics. Added the subsection "Source Properties" and 3 f
Scientific paper
10.1051/0004-6361:20053762
Strong gravitational lensing by irregular mass distributions, such as galaxy clusters, is generally not well quantified by cross sections of analytic mass models. Computationally expensive ray-tracing methods have so far been necessary for accurate cross-section calculations. We describe a fast, semi-analytic method here which is based on surface integrals over high-magnification regions in the lens plane and demonstrate that it yields reliable cross sections even for complex, asymmetric mass distributions. The method is faster than ray-tracing simulations by factors of $\sim30$ and thus suitable for large cosmological simulations, saving large amounts of computing time. We apply this method to a sample of galaxy cluster-sized dark matter haloes with simulated merger trees and show that cluster mergers approximately double the strong-lensing optical depth for lens redshifts $z_\mathrm{l}\gtrsim0.5$ and sources near $z_\mathrm{s} = 2$. We believe that this result hints at one possibility for understanding the recently detected high arcs abundance in clusters at moderate and high redshifts, and is thus worth further studies.
Bartelmann Matthias
Dolag Klaus
Fedeli Cosimo
Meneghetti Massimo
Moscardini Lauro
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