Cosmography with Cluster Strong Lensing

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This project will apply a novel technique in gravitational lensing to the measurement of fundamental parameters related to dark energy and the acceleration of the cosmic expansion. The focus is on strong gravitational lensing by massive clusters of galaxies. In strong lensing, the gravitational bending of light by the cluster produces multiple images of background galaxies. The new aspect to be explored in this project concerns those cases where there are multiple images of multiple sources at different distances behind the cluster. Because the lens is the same, analysis of the images can permit the extraction of the lens-source geometry, from which follow constraints on the overall cosmology. Applying this technique quantitatively requires good models for the mass distributions in galaxy clusters and along the full line of sight. To this end, the Principal Investigator and a supported graduate student will perform a ray-tracing analysis through cosmological structure-formation simulations, to quantify the expected statistical and systematic errors on the recovery of cosmological parameters from simulated lens systems. They will then apply the analysis to a sample of five cluster lenses, for which Hubble Space Telescope imaging data exist, and obtain joint constraints on the cosmological matter density and the dark-energy equation of state. In addition to advising the student supported by this project, the Principal Investigator will develop and teach a seminar in scientific communication for undergraduate astronomy majors. This course will jointly benefit university and K-12 students though the presentations that enrolled students will make to a high-school physics class.