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Department of Physics

Dr. Risa Wechsler
Stanford University
Risa Wechsler
The Dark Universe from Cosmological Surveys
102 Cardwell Hall
April 20, 2015
4:30 p.m. 


Measurements of the cosmos currently provide the most compelling evidence for physics beyond the standard model -- indicating a new matter component comprising 85% of the mass in the Universe (dark matter), and a new energy component that is driving the accelerating expansion of the Universe (dark energy). A new generation of cosmological sky surveys are being pursued to map out the matter distribution and its evolution over time, in order to test theories of dark energy and dark matter. I will describe first results from the Dark Energy Survey (DES), an imaging survey of 5000 sq. degrees that is now in its second year of a 5-year survey. Early results include the discovery of new dwarf galaxies in the Milky Way and the largest ever map of dark matter as probed by weak gravitational lensing. I will then describe the upcoming DESI and LSST surveys. The Dark Energy Spectroscopic Instrument (DESI) is a new 5000-fiber spectrograph that will pursue a large spectroscopic survey of 35 million galaxies over 14,000 sq. degrees.

The Large Synoptic Survey Telescope (LSST) is a new 3200 Megapixel camera, that will survey half of the sky every three nights, and map out the positions of 10 billion galaxies. I will discuss how these surveys can be used to better understand the nature of dark energy and dark matter, including the role of cosmological simulations and some of the theoretical challenges.