Probing Dark Energy with Strong Gravitational Lensing and LSST
Phil Marshall (SLAC)

Abstract:
Strong gravitational lenses have become an important astronomical tool: they allow us to make accurate measurements of galaxy masses, they provide a magnified view of the distant universe, and they allow us to constrain cosmological parameters. In particular, the time delays in multiply-imaged quasar systems enable measurements of distance in the Universe each with around 5% precision: I will review recent measurement of time delay distance in galaxy-scale lens systems. For us to realize the potential of this cosmological probe, we need to increase the size of our lens sample, and continue to improve the accuracy of its analysis. I will discuss the potential of the Large Synoptic Survey Telescope to provide a sample of several hundred lensed quasars with well-measured time delays that would enable competitive and complementary constraints on Dark Energy, and describe our ongoing investigations of how to find lenses, infer their time delays and model their mass distributions accurately, and account for weak lensing effects from external mass structures. This program lives in the LSST Dark Energy Science Collaboration, which is pursuing a high accuracy measurement of the Dark Energy equation of state parameters from 5 separate cosmological probes. I will give a brief update on recent activity in the LSST DESC, whose door is always open to new members.