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Durham University

Department of Physics

Staff profile

Publication details for Prof Richard Massey

Rhodes, J. & Massey, R. (2009), Weak Lensing in COSMOS, American Astronomical Society Meeting Abstracts 41: 214th American Astronomical Society Meeting. Pasadena, California, American Astronomical Society, 708.

Author(s) from Durham


Weak gravitational lensing, whereby the observed shapes of background galaxies are slightly distorted by foreground dark matter, is an ideal probe of both dark matter and dark energy. The 2 square degree COSMOS field was used to create the first high resolution, large-scale dark matter maps and definitively showed the growth of structure with cosmic time. We have since improved the COSMOS data and analysis in several key ways. Using both ground and space based data, we have significantly improved the accuracy of the photometric redshifts. We have developed a physically motivated algorithm to describe charge transfer in the HST ACS CCDs . Using this algorithm, we have also corrected the COSMOS images pixel by pixel for the image trailing induced by the degradation of charge transfer efficiency. This direct correction of the raw images offers significant improvement over the parametric correction of galaxy shapes in our previous analysis. These improvements in our analysis significantly reduce systematic errors in maps of the dark matter in the COSMOS field, and allow us to study the total mass profiles of groups and galaxies.