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Astron. Astrophys. 338, 777-780 (1998)


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Magnification cross-sections of gravitational lensing by galaxies in general FLRW cosmologies

Zong-Hong Zhu 1, 2

1 Institute of Theoretical Physics, Chinese Academy of Sciences, Beijing 100080, P.R. China
2 Beijing Astrophysics Center (BAC) *, Beijing, 100871, P.R. China

Received 7 April 1998 / Accepted 30 June 1998

Abstract

For a wide variety of cosmological models characterized by the cosmic mass density [FORMULA] and the normalized cosmological constant [FORMULA], we derive an analytic expression for the estimate of magnification cross-sections by an ensemble of isothermal spheres as models of galactic mass distributions. This provides a simple approach to demonstrate how the lensing probability by galaxies depends on the cosmological parameters. An immediate consequence is that, while a non-zero cosmological constant indeed leads to a significant increase of the lensing probability as it has been shown in the literature, only a small fraction of sky to [FORMULA] can be moderately ([FORMULA]) lensed by galaxies even in a [FORMULA]-dominated flat universe. Therefore, whether or not there is a nonzero cosmological constant, it is unlikely that the overall quasar counts have been seriously contaminated by the presence of galactic lenses.

Key words: gravitational lensing – galaxies: general

* BAC is jointly sponsored by The Chinese Academy of Sciences and Peking University

Send offprint requests to: Z.-H. Zhu 1

© European Southern Observatory (ESO) 1998

Online publication: September 17, 1998

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