Chuck Keeton (University of Chicago)
"Detecting Substructure with Strong Lensing"

ABSTRACT

The flux ratios between the images in 4-image lenses provide a powerful test of the smoothness of lens galaxy mass distributions. Many observed lenses have flux ratios incompatible with smooth models. Dalal & Kochanek (2002) used a Bayesian analysis to infer that some 2% of the mass in lens galaxies must lie in clumps, which they claim is a direct detection of substructure in quantities consistent with CDM and inconsistent with Warm Dark Matter. I will assess the current state of the data and theory and discuss future prospects on both fronts.

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