A gravitational lens probe of galaxy-scale dark matter?

Abstract

We present a model for an observed gravitationally lensed system, MG2016+112. We assume that there are two galaxies acting as lenses (as suggested by the observations), each with a diffuse dark matter halo. It is shown that the two lenses, acting in tandem, can conspire to produce the image configurations observed on both arcsecond and milliarcsecond scales. The dark matter halos, each of which is a weak lens, overlap in projection. This increases the strength of the lens system, making MG2016+112 a potential probe of diffuse dark matter in galaxies. It is possible to account for some additional, rather puzzling observations. We show, finally, that the galaxy-plus-halo structures that are suggested by our model are consistent with observations of single lens galaxy-scale systems