SCIENCE

Targeting the search

The wide-field Sloan Telescope covers a wide expanse of sky at moderate magnification. To measure both galaxies and quasars, a thousand targets for each BOSS exposure are selected in advance from existing surveys. At the telescope’s focal plane, “plug plates” are precision-machine-drilled with tiny holes at positions of known galaxies and quasars. These holes are plugged with optical fibers that channel the light from each chosen galaxy or quasar to a spectrograph, which isolates the spectrum of each individual object. Schlegel credits Berkeley Lab’s Nicholas Ross for doing much of the “incredibly hard work” involved in this targeting.

Slosar says, “Our exploratory paper includes less than a tenth of the 160,000 quasars that BOSS will study, but already that’s enough to establish a proof of the concept. This is a potentially revolutionary technique for mapping the very distant universe. We’re paving the way for future BAO experiments like BigBOSS to follow suit.” BigBOSS is a proposed survey that will find precise locations for 20 million galaxies and quasars and go beyond BOSS to encompass 10 times the volume of the finished BOSS map.

“By the time BOSS ends, we will be able to measure how fast the universe was expanding 11 billion years ago with an accuracy of a couple of percent,” says Patrick McDonald of Berkeley Lab and Brookhaven, who pioneered techniques for measuring the universe with the Lyman-alpha forest. “Considering that no one has ever measured the cosmic expansion rate so far back in time, that’s a pretty astonishing prospect.”

Says Slosar, “We now know we can use the Lyman-alpha forest to look at the dark energy. There is all this structure at the distant universe that has never been seen before. Sometimes I feel like an adventuring cartographer from the Middle Ages!”

“The Lyman-α forest in three dimensions: measurements of large scale flux correlations from BOSS 1st-year data,” by Anže Slosar, Andreu Font-Ribera, Matthew M. Pieri, James Rich, Jean-Marc Le Goff, Eric Auburg, J. Brinkmann, Nicolas Busca, Bill Carithers, Romain Charlassier, Marina Cortês, Rupert Croft, Kyle S. Dawson, Jean-Christophe Hamilton, Shirley Ho, Khee-Gan Lee, Patrick McDonald, Bumbarija Medolin, Jordi Miralda-Escudé, Adam D. Myers, Robert C. Nichol, Nathalie Palanque-Delabrouille, Isabelle Pâris, Patrick Petitjean, Yodovina Piškur, Emmanuel Rollinde, Nicholas P. Ross, David J. Schlegel, Donald P. Schneider, Erin Sheldon, Benjamin A. Weaver, David Weinberg, Christophe Yeche, and Don York will be available online at http://arxiv.org/abs/1104.5244.

Funding for SDSS-III has been provided by the Alfred P. Sloan Foundation, the Participating Institutions, the National Science Foundation, and the U.S. Department of Energy’s Office of Science. The SDSS-III web site is http://www.sdss3.org/. SDSS-III is managed by the Astrophysical Research Consortium for the Participating Institutions of the SDSS-III Collaboration including the University of Arizona, the Brazilian Participation Group, Brookhaven National Laboratory, University of Cambridge, University of Florida, the French Participation Group, the German Participation Group, the Instituto de Astrofisica de Canarias, the Michigan State/Notre Dame/JINA Participation Group, Johns Hopkins University, Lawrence Berkeley National Laboratory, Max Planck Institute for Astrophysics, New Mexico State University, New York University, Ohio State University, Pennsylvania State University, University of Portsmouth, Princeton University, the Spanish Participation Group, University of Tokyo, University of Utah, Vanderbilt University, University of Virginia, University of Washington, and Yale University.

Lawrence Berkeley National Laboratory addresses the world’s most urgent scientific challenges by advancing sustainable energy, protecting human health, creating new materials, and revealing the origin and fate of the universe. Founded in 1931, Berkeley Lab’s scientific expertise has been recognized with 12 Nobel prizes. The University of California manages Berkeley Lab for the U.S. Department of Energy’s Office of Science. For more, visit www.lbl.gov.