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Lensing Statistics with Realistic Galaxy Models:
Eects on the Cosmological Constraints
David Rusin
University of Pennsylvania, USA
Gravitational lensing oers a potentially powerful tool for con-
straining the cosmological density parameters, particularly the
cosmological
constant(
 ). This is accomplished by compar-
ing the observed lensing rate with the predictions of various cos-
mologies. The recently completed Cosmic Lens All-Sky Survey
(CLASS), the most ambitious and successful lens survey to date,
gives us the raw materials we need to approach this problem { a
large well-dened and observationally unbiased radio sample that
includes  20 new lens systems. The introduction of advanced
analysis techniques is required to make the most of this data and
assess the reliability of the derived cosmological constraints. Sig-
nicant computational improvements are achieved with a more
realistic representation of galaxy mass distributions. In previous
analyses of lens surveys, it has been common to model galaxies as
a population of non-evolving spherical (and sometimes singular)
isothermal de ectors. This over-simplication can lead to large
systematic errors in the predicted lensing rate. Here we present a
series of advanced calculations of the lensing optical depth which
includes the contributions of halo ellipticity, core radii and evo-
lution of the galaxy luminosity function. We use these results to
update constraints
on
 from previous lens surveys, while setting
the stage for a complete statistical analysis of CLASS.
Co-author: Max Tegmark
1