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New 3-D Map of Massive Galaxies and Distant Black Holes Offers Clues to Dark Matter and Dark Energy

The Sloan Digital Sky Survey III (SDSS-III) has released the largest-ever three-dimensional map of massive galaxies and distant black holes, which will help astronomers explain the mysterious "dark matter" and "dark energy" that scientists know makes up 96 percent of the Universe.

Early last year, the SDSS-III released the largest-ever image of the sky. With the new release of data, SDSS-III has begun to expand this image into a full three-dimensional map. Data Release 9 (DR9), posted online last week, makes available the first third of the galaxy map that this six-year project will create.

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A video fly-through of the SDSS-III galaxies mapped in Data Release 9. Click on the image to play the video, or select one of the Download Movie options above to download.

Each galaxy in the animation is placed at the location mapped by SDSS and is represented by the zoomed-in template image that matches the actual shape of the galaxy.

Galaxies are concentrated into clusters and filaments with voids in between. The SDSS-III is exploring this structure to determine the nature of dark energy and the distribution of dark matter in the Universe.

Credit: Miguel A. Aragón (Johns Hopkins University), Mark SubbaRao (Adler Planetarium), Alex Szalay (Johns Hopkins University), Yushu Yao (Lawrence Berkeley National Laboratory, NERSC), and the SDSS-III Collaboration

There is also a 3-D version of the movie available - it uses traditional red/blue movie theater glasses.

"What really makes me proud of this survey is our commitment to creating a legacy for the future," said Michael Blanton, a professor at New York University who led the team that prepared DR9. "Our goal is to create a map of the Universe that will be used long after we are done, by future generations of astronomers, physicists and the general public."

Data Release 9 is the latest in a series of data releases stretching back to 2001. This release includes new data from the ongoing SDSS-III Baryon Oscillation Spectroscopic Survey (BOSS), which will eventually measure the positions of 1.5 million massive galaxies over the past six billion years of cosmic time, as well as 160,000 quasars — giant black holes actively feeding on stars and gas — from as long ago as 12 billion years in the past.

With such a map, scientists can retrace the history of the Universe over the last six billion years. With that history, they can get better estimates for how much of the Universe is made up of dark matter - matter that we can't directly see because it doesn't emit or absorb light - and dark energy, the even more mysterious force that drives the accelerating expansion of the Universe.

"Dark matter and dark energy are two of the greatest mysteries of our time," said David Schlegel of Lawrence Berkeley National Laboratory, who led the SDSS-III effort to map these galaxies and quasars. "We're confident this new map will guide us, or someone else, in solving these mysteries."

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The SDSS spectroscopic plate is a
			disk about one meter across with more than 600 tiny holes drilled

The hardware that the SDSS used to measure distances to the thousands of galaxies in Data Release 9.

The bottom image shows The Sloan Foundation Telescope. The top left image shows the meter-wide aluminum plate that the SDSS uses to measure the spectra of a thousand galaxies at a time. Each hole in the plate matches the position of a star or galaxy. A fiber optic cable (red and blue in the bottom image) connects each hole to the SDSS spectrograph. Markings on the plate (visible in the close-up view in the center-right) aid with the hand-plugging of the fibers.

Credit: Paul Preuss (Lawrence Berkeley National Laboratory), Dan Long (Apache Point Observatory), and the SDSS-III Collaboration

That map of the Universe is the centerpiece of DR9. It includes new spectra from 540,000 galaxies from when the Universe was half its present age. A spectrum is a measure of light from a galaxy at different wavelengths; from this information we can measure the distances to those galaxies. This distance information provides the third dimension in the DR9 map, providing a more detailed view of the structure of the Universe than has been measured before.

Quasars provide further details to the three dimensional map and another way to measure the distribution of matter in the Universe. Quasars are the brightest objects in the distant Universe, and their spectra reveal intricate patterns imprinted by the intergalactic gas and underlying dark matter that lies between each quasar and the Earth.

The new data in DR9 are not only helping us understand the distant Universe, but also our own cosmic backyard, the Milky Way galaxy. DR9 includes better estimates for the chemical compositions of more than half a million stars in our own galaxy. "With these better estimates, we can look back at the history of our galaxy," said Connie Rockosi of the University of California Santa Cruz, who leads the SDSS- III's Milky Way study. "This new information can help us tell the story of how our galaxy formed, and how it came to be the Milky Way that we see today."

All these new images and spectra contain the promise of new discoveries about our Universe -- but the SDSS-III is only in the middle of its six-year survey, and will release three times as much data by the time it's completed in 2014.

"The most fun part of making this data available online is knowing that anyone on the Internet can now access the very same data and search tools that professional astronomers use to make exciting discoveries about our Universe," said Ani Thakar of Johns Hopkins University, a key member of the data team who works hard behind-the-scenes to distribute the terabytes of SDSS-III data to astronomers and the public through these data releases.

And DR9 doubtless contains many surprises.

"This is science at its collaborative best. SDSS-III scientists work together to address big questions extending from our own galaxy to distant reaches of the Universe -- and then they share all of that data with the world to allow anyone to make the next big discovery," said Michael Wood-Vasey, a professor at the University of Pittsburgh and the Scientific Spokesperson for the SDSS-III collaboration.

All the data are available now on the Data Release 9 website. The new data are being made available to astronomers, as well as students, teachers, and the public. The SkyServer website includes lesson plans for teachers that use DR9 data to teach astronomy and other topics in science, technology, and math. DR9 data will also feature in a new release of the Galaxy Zoo citizen science project, which will allow online volunteers to contribute to cutting-edge astronomy research.


Published Paper for Data Release 9

SDSS-III Collaboration: Ahn C. P. et al. 2012, The Ninth Data Release of the Sloan Digital Sky Survey: First Spectroscopic Data from the SDSS-III Baryon Oscillation Spectroscopic Survey, submitted to Astrophysical Journal Supplement Series and available on the arXiv preprint server (1207.7137).



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 Office of Science. The SDSS-III web site is

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, Carnegie Mellon University, University of Florida, the French Participation Group, the German Participation Group, Harvard University, 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, Max Planck Institute for Extraterrestrial Physics, 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.