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June 15 at 11:00AM in the 2nd Floor Conference Room in Dearborn Speaker: Sherry Suyu (University of Bonn) “Dissecting the Gravitational Lens B1608+656: Implications for the Hubble Constant” Strong gravitational lens systems provide a tool for probing galaxy mass distributions (independent of their light profiles) and for measuring cosmological parameters. One can use lens systems to measure the Hubble constant by obtaining the relative time delays between the multiple images and modeling the lens potential. B1608 +656 is a 4-image gravitational lens system with an extended source intensity distribution and two interacting galaxy lenses. This system is special in that the three relative time delays between the four images were measured accurately with errors of only a few percent, and it thus provides an opportunity to measure the Hubble constant with high precision. I will present a comprehensive Bayesian analysis of B1608+656 incorporating (i) deep HST observations, (ii) a new velocity dispersion measurement of the primary lens galaxy, (iii) lens environment studies, and (iv) time delay measurements. Based on a pixelated lens potential reconstruction method, our lensing analysis of the HST observations takes into account the effects of the extended source intensity distribution, dust extinction, and interacting lens galaxies. In combination with the dynamics modeling of the primary lens galaxy and lens environment studies, we break the mass-sheet degeneracy in lensing. I will show preliminary results on the implications for the Hubble constant from B1608+656. |