Speaker: Thomas Collett

Ongoing and future imaging surveys represent significant improvements in depth, area, and seeing compared to current data sets. These improvements offer the opportunity to discover up to three orders of magnitude more galaxy-galaxy strong lenses than are currently known. In this talk I will make forecasts for the number of lenses discoverable in DES, LSST and Euclid and the properties of these lens populations. I’ll also talk about the population of compound lenses discoverable in the Universe and present an investigation into the image multiplicities and arc morphologies possible in these systems. Discovering these systems will be hard, but will open up new avenues to investigate cosmological parameters, mass distributions in lenses and high redshift sources.

Initial efforts to discover strong lenses in the Dark Energy Survey have resulted in the discovery of a strong lensing cluster at redshift 1. This system is exciting since few clusters are known at high redshift and strong lensing offers the only practicable method to probe the lens mass distribution at these redshifts. The arc system is also exotic as it includes a bright central image; the central image is indicative of a flat central density profile. I will report on lens modelling of this system which conclusively shows that the dark matter profile of the lens has a giant core of 50 kpc radius, in tension with the NFW profile predicted by CDM simulations.