Determining the Relation between Dark and Luminous Matter: SDSS Weak Lensing Studies

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AST-0206277McKay, Timothy A.Models of hierarchical structure formation based on N-body simulations now provide a relatively complete picture of the formation, evolution, and clustering properties of darkmatter halos around galaxies. Unfortunately, experimental determination of structure relies on observations of luminous galaxies, whose formation involves gas dynamics, star formation, and the feedback of entropy into the interstellar medium. These processes are complex, hampering direct simulation. As a result, the detailed relationship between luminous galaxies and their dark matter environments (the "bias") is poorly determined.This uncertainty seriously limits our ability to compare cosmological observations of galaxies to theoretical models. This program will conduct a closely coordinated observational and theoretical study of the relationship between luminous galaxies and their dark matter environments. McKay and his students will pursue weak lensing measurements within the Sloan Digital Sky Survey, while Evrard and Wechsler will make parallel measurements within N-body simulations. This will allow direct comparison of theory and observation at the level of the fundamental observables, without recourse to intermediate model fitting. By comparing lensing measurements to parallel studies of simulations this work will probe bias in new ways.***