The statistical era of strong gravitational lensing cosmology

Strong gravitational lensing is on the cusp of a new era. Strong lensing occurs when the mass of a galaxy deforms space time so much that multiple images of a single background source is observed. Strong lensing is a powerful cosmological probe, but it is hamstrung by sample size: currently we only know of a few hundred systems. I am leading the work on a new telescope, the Large Synoptic Survey Telescope, which in its first year will observe more of the optical Universe than all previous telescopes combined. This revolutionary dataset will transform strong lensing into a statistical science by enabling LensEra to discover 30,000 new lenses and exploit them for cosmology.The first objective of LensEra uses machine learning, citizen science and automated lens modelling to build a discovery engine to find 30,000 new lenses in the Large Synoptic Survey Telescope data, including 600 lenses with multiple background sources, and 300 lensed supernovae. LensEra will then confirm these using the 4MOST multi-object spectroscopic survey and the robotic Liverpool Telescope.The second objective of LensEra develops 3 new tests of cosmology using rare subsets of the lens population: measuring the expansion of the Universe with samples of lensed supernovae; measuring the equation of state of dark energy with lenses with multiple background sources; and, testing the validity of General Relativity with lensing combined with stellar kinematics. The new sample from the first objective will allow LensEra to launch strong lensing cosmology into a new statistical age. Combining detailed analysis of ~200 golden lenses (the best LSST lensed supernovae and brightest double source plane lenses) with an automated modelling of the full sample will enable precise and accurate cosmological inference.