Issue |
A&A
Volume 447, Number 2, February IV 2006
|
|
---|---|---|
Page(s) | 419 - 430 | |
Section | Cosmology (including clusters of galaxies) | |
DOI | https://doi.org/10.1051/0004-6361:20053762 | |
Published online | 07 February 2006 |
A fast method for computing strong-lensing cross sections: application to merging clusters
1
Zentrum für Astronomie, ITA, Universität Heidelberg, Albert-Überle-Str. 2, 69120 Heidelberg, Germany e-mail: cosimo@ita.uni-heidelberg.de
2
Dipartimento di Astronomia, Università di Bologna, via Ranzani 1, 40127 Bologna, Italy
3
Max-Planck-Institut für Astrophysik, Karl-Schwarzschild-Str. 1, 85740 Garching, Germany
Received:
5
July
2005
Accepted:
28
September
2005
Strong gravitational lensing by irregular mass distributions,
such as galaxy clusters, is generally not quantified well 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 that 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 ~30 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 and sources
near
. 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 studying further.
Key words: gravitational lensing / galaxies: clusters: general / dark matter
© ESO, 2006
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