Gravitational Lensing as a Probe of Cold Dark Matter Subhalos
Figure 5
Astrometric perturbations. (a) One of the multiple sightlines towards a distant light source passes through a dark subhalo. (b) The images of the macrolensed source are observed at the positions of the gray source symbols. Modelling of the lens system with a smooth lens potential predicts the position of the upper image at the white source symbol. The subhalo close to the sightline of the image causes a deflection on the order of a few tens of milliarcseconds.
