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Research @ KICP
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Research Highlight October 20, 2004 Sloan Digital Sky Survey uses gravitational lensing to compare the distributions by Erin Sheldon ![]() The Sloan Digital Sky Survey (SDSS), the most ambitious project to map the Universe ever undertaken, has measured images for tens of millions of galaxies and three-dimensional positions (using redshifts obtained from spectra of these galaxies) of about 500,000 objects to date. The project uses a dedicated 2.5-meter telescope in southern New Mexico. One recent highlight of the project was the measurement of the halos of dark matter that surround luminous galaxies by KICP Fellow Erin Sheldon, former KICP graduate student David Johnston (now a postdoctoral fellow at Princeton) and KICP faculty member Josh Frieman, and their collaborators. This measurement used the relatively new technique of weak gravitational lensing: the shapes of about 8 million distant galaxies were measured and used to infer the mass distribution around 100,000 foreground galaxies. As the light from the distant galaxies passes by the foreground galaxies, it is bent by their gravitational fields, leading to a small distortion of the shapes of the background galaxies. Measuring that distortion allows one to make inferences about the halos of dark matter in which the foreground galaxies are enshrouded. A paper describing these results appeared in the May 2004 issue of the Astronomical Journal and at <a target='_blank' href='http://xxx.lanl.gov/abs/astro-ph/0312036'>Astrophysics abstracts</a>. ![]() Related Links: KICP Members: Joshua A. Frieman; Erin S. Sheldon Scientific projects: Sloan Digital Sky Survey (SDSS) |