Evolution of Dark Matter with Weak Gravitational Lensing

University Of Pennsylvania, Philadelphia PA

Investigators

Abstract

AST-0236702 Bernstein, Gary M. The Universe is believed to consist primarily of dark matter, some unknown substance that makes its presence known only by its gravitational effects. Among these effects is the deflection of starlight, also known as gravitational lensing: objects seen behind a dark matter concentration will have their appearance distorted as the light rays pass the dark matter. In some cases this lensing distortion is dramatic, but our view of nearly every galaxy in the Universe is distorted to a very small degree by intervening dark matter. By measuring these weak gravitational lensing effects, one can map the distribution of the dark matter. The distortion typically amounts to a <1% elongation of a background galaxy, so exploitation of weak gravitational lensing requires the astronomer to measure 100,000 to 10,000,000 galaxy shapes, and to pay careful attention to slight optical defects that can mimic gravitational lensing. The rewards are great, however, since the ability to "see" dark matter can answer many of the most important questions about the Universe. The work under this grant will apply new techniques to the analysis of weak lensing data, and advance the precision of these measurements to the few-percent level using data being gathered by the Deep Lens Survey and other large imaging surveys. With these data it will be possible to plot the evolution of dark matter halos around galaxies since redshift 0.5. Other existing and new data will be analyzed to map the dark matter in massive galaxy clusters. ***