The Deep Lens Survey now in progress will provide a much stricter test of cosmological models, or suggest the need for new models. The images were stacked and convolved again to eliminate any PSF anisotropy due to slight registration errors. Angular correlations of galaxy ellipticity in each field revealed a signature of weak gravitational lensing by large-scale structure. Three other groups subsequently submitted cosmic shear papers in agreement with this measurement. The indication of a low matter universe is in agreement with a remarkable array of independent observations, including high-redshift supernovae and the cosmic microwave background.
Surveys are now underway to improve the accuracy of cosmic shear measurements.
Comparison of improved CMB and cosmic shear measurements will provide stringent tests of the underlying assumptions in cosmology and perhaps suggest new models. With a total exposure time of 18,000 seconds in R and 12,000 seconds in BRz', the group will assign photometric redshifts to source galaxies and study the evolution of structure over time by separating the sources into discrete redshift bins on the order of 0.3 in z. The first observing season is done, with 19 of the total of 86 nights completed.