Cosmic Gravitational Shear from the Hubble Space Telescope Medium Deep Survey

Abstract

We present a measurement of cosmic shear on scales ranging from 10" to 2' in 347 Wide Field Planetary Camera 2 (WFPC2) images of random fields. Our result is based on shapes measured via image fitting and on a simple statistical technique; careful calibration of each step allows us to quantify our systematic uncertainties and to measure the cosmic shear down to very small angular scales. The WFPC2 images provide a robust measurement of the cosmic shear signal decreasing from 5.2% at 10" to 2.2% at 130".