Astronomy Colloquium - Risa Wechsler
- Risa Wechsler
- Stanford University
A new generation of sky surveys are beginning to map the universe’s expansion history and evolution of structure over the last ~ 12 billion years, using statistical constraints from hundreds of millions of galaxies. I will present cosmological constraints from a combined analysis of galaxy clustering and weak gravitational lensing, using 1321 deg^2 of griz imaging data from the first year of the Dark Energy Survey. The analysis combines (i) the cosmic shear correlation function of 26 million source galaxies in four redshift bins, (ii) the galaxy angular autocorrelation function of 650,000 luminous red galaxies in five redshift bins, and (iii) the galaxy-shear cross-correlation of luminous red galaxy positions and source galaxy shears. These three measurements yield consistent cosmological results, and provide constraints on the amplitude of density fluctuations and dark energy equation of state that are competitive with those from Planck cosmic microwave background measurements. I will also describe the extensive validation of the measurements and modeling, with a particular focus on the role of cosmological simulations and modeling of the connection between galaxies and dark matter, highlighting where these efforts will need to go in the future to keep up with the exciting cosmological measurements expected from DES, DESI, LSST and other future galaxy surveys.