Background, foreground and nearby matter influence on strong gravitational lenses

摘要: We investigate strong lensing by non-singular finite isothermal ellipsoids taking into account the influence of matter along line sight and in close lens vicinity. compare three descriptions light propagation: full approach all inhomogeneities rays; single plane approach, where we take neighbours but neglect foreground background objects; approach. In each case, simulate many configurations placing a point source at same redshift different locations inside region surrounded caustics. further analyse four or five images. For every simulated configuration, attempt to fit simplified model using ellipsoid with external shear. The fits obtained are rejected majority cases 95 per cent significance. rejection rate is substantially lower. Also inclusion shear modelling improves chances obtaining acceptable fits, problem not solved completely. quantitative estimates rates models depend on required accuracy models, present few illustrative examples, which show that both rays do have important modelling. also estimate typical value fitted parameters lenses used simulations.