Description: | Strong gravitational lenses provide by far the best probe of the mass structure and evolution of early-type galaxies to redshifts of unity and beyond. I will present the ideas behind lensing (i.e. why it works), complex lens modeling techniques that we have been developing over the last years, and several recent results from the Sloan Lens ACS (SLACS) survey, using HST and the VLT. I will conclude with a future outlook.
Above: Images by Hubble Space Telescope. The colors of the foreground elliptical galaxies have been assigned based upon the g-r colors measured by the SDSS, and the lensed background-galaxy features have been enhanced in blue. The left panel in each cell shows the Hubble data, while the right panel shows a mathematical model used to describe the foreground and background galaxies, including the lensing effect that distorts the image of the latter. The foreground and background redshifts in each system are given as z1 and z2 respectively.
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