Weak Lensing by Large-Scale Structure with the FIRST Radio Survey

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The coherent image distortions induced by weak gravitational lensing can be used to measure the power spectrum of density inhomogeneities in the universe. We present our on-going effort to detect this effect with the FIRST radio survey, which currently contains about 400,000 sources over 4,200 square degrees, and thus provides a unique resource for this purpose. We discuss the sensitivity of our measurement in the context of various cosmological models. We then discuss the crucial issue of systematic effects, the most serious of which are source fragmentation, image-noise correlation, and VLA-beam anisotropy. After accounting for these effects, we expect our experiment to yield a detection, or at least a tight upper limit, for the weak lensing power spectrum on 0.2-20 degree scales.