2001/01/21 by Premana Premadi, Premana W. Premadi, Hugo Martel +4 · 5 citations
Physics and Astronomy · #Cosmology and Gravitation Theories #Dark Matter and Cosmic Phenomena #Galaxies: Formation, Evolution, Phenomena #astro-ph
paper · pdf · doi:10.1086/321776
published as Astrophys.J.Suppl. 135 (2001) 7-40 · 45 pages, including 23 figures, Accepted for publication in The Astrophysical Journal Supplement
arxiv created 2001/01/21 · openalex publication_date 2001/07/01 · arxiv updated 2009/12/01 · openalex created_date 2025/10/10 · openalex updated_date 2026/07/31
Using a multiple lens-plane algorithm, we study light propagation in inhomogeneous universes, for 43 different COBE -normalized cold dark matter models, with various values of the density parameter Ω 0 , cosmological constant λ 0 , Hubble constant H 0 , and rms density fluctuation σ 8 . This is the largest cosmological parameter survey ever undertaken in this field. We performed a total of 3798 experiments, each experiment consisting of propagating a square beam of angular size 21 9 × 21 9 composed of 116,281 light rays from the observer up to redshift z = 3. These experiments provide statistics of the magnification, shear, and multiple imaging of distant sources. The results of these experiments can be compared with observations and eventually help to constrain the possible values of the cosmological parameters. In addition, they provide insight into the gravitational lensing process and its complex relationship with the various cosmological parameters. Our main results are the following: (1) The magnification distribution depends mostly upon λ 0 and σ 8 . As σ 8 increases, the low tail of the magnification distribution shifts toward lower magnifications, while the high tail is hardly affected. The magnification distribution also becomes wider as λ 0 increases. This effect is particularly large for models with λ 0 = 0.8. (2) The magnification probability P m is almost independent of σ 8 , for any combination of Ω 0 , λ 0 , and H 0 , indicating that P m does not depend strongly upon the amount of large-scale structure. (3) The shear distribution, like the magnification distribution, depends mostly upon λ 0 and σ 8 . The shear distribution becomes wider with increasing σ 8 and increasing λ 0 . The similarities between the properties of the magnification and shear distributions suggest that both phenomena are caused by weak lensing. (4) About 0.3% of sources have multiple images. The double-image probability P 2 increases strongly with λ 0 and is independent of Ω 0 , H 0 , and σ 8 . (5) The distribution of image separations depends strongly upon λ 0 and is independent of σ 8 . Summarizing these results, we find that ( a ) The properties of gravitational lensing, both weak and strong, depend much more strongly upon λ 0 than any other cosmological parameter, and ( b ) magnification and shear are examples of weak lensing caused primarily by the distribution of background matter, with negligible contribution from galaxies, while multiple images and rings are examples of strong lensing, caused by direct interaction with galaxies, with negligible contribution from the background matter. Observations of weak lensing can be used to determine the cosmological constant and the density structure of the universe, while observations of strong lensing can be used to determine the cosmological constant and the internal structure of galaxies and clusters. Gravitational lensing depends much more weakly upon Ω 0 and H 0 than σ 8 and λ 0 , making a determination of these parameters from observations more difficult.