Astronomy and Astrophysics – Astrophysics
Scientific paper
2002-01-12
Astronomy and Astrophysics
Astrophysics
One Plain TeX file, with 12 postscript figures. Accepted for publication in The Astrophysical Journal
Scientific paper
10.1086/339569
Using an analytical model, we compute the distribution of image separations resulting from gravitational lensing of distant sources, for 7 COBE-normalized CDM models with various combinations of Omega_0 and lambda_0. Our model assumes that multiple imaging results from strong lensing by individual galaxies. We model galaxies as nonsingular isothermal spheres, and take into account the finite angular size of the sources. Our model neglects the contribution of the background matter distribution, and assumes that lensing is entirely caused by galaxies. To test the validity of this assumption, we performed a series of ray-tracing experiments to study the effect of the background matter on the distribution of image separations. The analytical model predicts that the distributions of image separations are virtually indistinguishable for flat, cosmological constant models with different values of Omega_0. For models with no cosmological constant, the distributions of image separations do depend upon Omega_0, but this dependence is weak. We conclude that while the number of multiple-imaged sources can put strong constraints on the cosmological parameters, the distribution of image separations does not constrain the cosmological models in any significant way, and mostly provides constraints on the structure of the galaxies responsible for lensing.
Martel Hugo
Matzner Richard
Premadi Premana
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