Cosmology with Gravitational Lens Time Delays: Past, Present and Future / Dr Sherry Suyu (Institute of Astronomy & Astrophysics, Academia Sinica)

Abstract
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Strong gravitational lensing occurs when two objects are closely aligned along the line of sight so that the light from the background object (the source) is bent by the foreground object (the lens) and forms multiple images.  Strong gravitational lens systems with measured time delays between the multiple images can be used to determine the "time-delay distance" to the lens, which is primarily sensitive to the Hubble constant.  I will describe the ingredients and newly developed techniques for measuring accurately time-delay distances with a realistic account of systematic uncertainties.  A program initiated to measure the Hubble constant to <4% in precision from gravitational lens time delays is in progress, and I will present the first results and their implications.  I will show the bright prospects of gravitational lens time delays as an independent and competitive cosmological probe.