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Large current and future surveys, like the Two degree Field survey (2dF), the Sloan Digital Sky Survey (SDSS) and the proposed Kilo-Degree Survey (KIDS) are likely to provide us with many new strong gravitational lenses. Taking cosmological parameters as known, we calculate the expected lensing statistics of the galaxy population in large, low-redshift(More)
We discuss strong gravitational lensing by multiple objects along any line of sight. The probability for strong gravitational lensing by more than one lens is small, but a number of strong lens systems in which more than one separate lens contribute significantly to the lensing potential will be detected in the large sample of lens systems compiled with new(More)
We investigate gravitational lensing by a realistic model of disk galaxies. Most of the mass is contained in a large spherical isothermal dark matter halo, but the potential is modified significantly in the core by a gravitationally-dominant exponential disk. The method used is adapted from a very general multi-lens ray-tracing technique developed by(More)
In the CDM scenario, dark matter halos are assembled hierarchically from smaller subunits. A long-standing problem with this picture is that the number of sub-halos predicted by CDM simulations is orders of magnitudes higher than the known number of satellite galaxies in the vicinity of the Milky Way. A plausible way out of this problem could be that the(More)
In this paper the expected properties of the velocity fields of strongly lensed arcs behind galaxy clusters are investigated. The velocity profile along typical lensed arcs is determined by ray tracing light rays from a model source galaxy through parametric cluster toy-models consisting of individual galaxies embedded in a dark cluster halo. We find that(More)
There are a number of theoretical and observational hints that large numbers of lowmass galaxies composed entirely of dark matter exist in the field. The theoretical considerations follow from the prediction of cold dark matter theory that there exist many low-mass galaxies for every massive one. The observational considerations follow from the observed(More)
In this paper, we study gravitational lensing by groups of galaxies. Since groups are abundant and therefore have a large covering fraction on the sky, lensing by groups is likely to be very important observationally. Besides, it has recently become clear that many lens models for strong lensing by individual galaxies require external shear to reproduce the(More)
The high-magnification gravitational lensing cross-section of a galaxy is enhanced significantly if a baryonic disc is embedded in its dark matter halo. We investigate the effects of a population of such discs on the probability of detecting strongly lensed images of distant galaxies and quasars. The optical depth to lensing is always more than doubled. The(More)