Strong Gravitational Lensing By Clusters of Galaxies: Theory, Surveys, and Observations
Joe Hennawi (UC Berkeley)
Does the currently favored LCDM cosmological model explain the detailed distribution of dark matter in galaxy clusters? Now that the initial conditions for structure formation are known from WMAP, cosmological N-body simulations predict the structure of dark matter halos ab initio. Strong gravitational lensing provides a powerful test of LCDM, probing the dense cluster core where mass to light ratios are high and dark matter dominates over baryons. I will describe how cosmological ray-tracing simulations can be used to provide detailed predictions for the statistics of cluster lensing. I will review recent work highlighting potential conflicts with the CDM paradigm; but his tension is based on only a handful of well studied systems. To improve the statistics, we have undertaken the SDSS Giant Arc Survey, an imaging campaign using 2-4m class telescopes, to search for lenses in the 6 Gpc^3 volume of the SDSS. This ongoing survey effort has already increased the number of lensing clusters by an order of magnitude. I will describe the survey strategy, dedicated follow-up on 6-8m telescopes, and some early results.
Joe Hennawi (UC Berkeley)
Does the currently favored LCDM cosmological model explain the detailed distribution of dark matter in galaxy clusters? Now that the initial conditions for structure formation are known from WMAP, cosmological N-body simulations predict the structure of dark matter halos ab initio. Strong gravitational lensing provides a powerful test of LCDM, probing the dense cluster core where mass to light ratios are high and dark matter dominates over baryons. I will describe how cosmological ray-tracing simulations can be used to provide detailed predictions for the statistics of cluster lensing. I will review recent work highlighting potential conflicts with the CDM paradigm; but his tension is based on only a handful of well studied systems. To improve the statistics, we have undertaken the SDSS Giant Arc Survey, an imaging campaign using 2-4m class telescopes, to search for lenses in the 6 Gpc^3 volume of the SDSS. This ongoing survey effort has already increased the number of lensing clusters by an order of magnitude. I will describe the survey strategy, dedicated follow-up on 6-8m telescopes, and some early results.