3D Map of Universe Bolsters Case for Dark Energy and Dark Matter(Forwarded)

Sloan Digital Sky Survey

CONTACTS:
Prof. Max Tegmark, Univ. of Pennsylvania
215-898-5942,

Prof. Michael Strauss, Princeton University
609-258-3808,

Dr. Michael Blanton, New York University
212-992-8791,

Gary S. Ruderman, Public Information Officer
The Sloan Digital Sky Survey
312-320-4794 (cell),

October 27, 2003

3D Map of Universe Bolsters Case for Dark Energy and Dark Matter

Astronomers from the Sloan Digital Sky Survey (SDSS) have made the most precise
measurement to date of the cosmic clustering of galaxies and dark matter,
refining our understanding of the structure and evolution of the Universe.

"From the outset of the project in the late 80's, one of our key goals has been
a precision measurement of how galaxies cluster under the influence of gravity",
explained Richard Kron, SDSS's director and a professor at The University of
Chicago.

SDSS Project spokesperson Michael Strauss from Princeton University and one of
the lead authors on the new study elaborated that: "This clustering pattern
encodes information about both invisible matter pulling on the galaxies and
about the seed fluctuations that emerged from the Big Bang."

The findings are described in two papers submitted to the Astrophysical Journal
and to the Physical review D; they can be found on the physics preprint Web
site, www.arXiv.org, on October 28.

MAPPING FLUCTUATIONS

The leading cosmological model invokes a rapid expansion of space known as
inflation that stretched microscopic quantum fluctuations in the fiery aftermath
of the Big Bang to enormous scales. After inflation ended, gravity caused these
seed fluctuations to grow into the galaxies and the galaxy clustering patterns
observed in the SDSS.

Images of these seed fluctuations were released from the Wilkinson Microwave
Anisotropy Probe (WMAP) in February, which measured the fluctuations in the
relic radiation from the early Universe.

"We have made the best three-dimensional map of the Universe to date, mapping
over 200,000 galaxies up to two billion light years away over six percent of the
sky", said another lead author of the study, Michael Blanton from New York
University. The gravitational clustering patterns in this map reveal the makeup
of the Universe from its gravitational effects and, by combining their
measurements with that from WMAP, the SDSS team measured the cosmic matter to
consist of 70 percent dark energy, 25 percent dark matter and five percent
ordinary matter.

They found that neutrinos couldn't be a major constituent of the dark matter,
putting among the strongest constraints to date on their mass. Finally, the SDSS
research found that the data are consistent with the detailed predictions of the
inflation model.

COSMIC CONFIRMATION

These numbers provide a powerful confirmation of those reported by the WMAP
team. The inclusion of the new SDSS findings helps to improve measurement
accuracy, more than halving the uncertainties from WMAP on the cosmic matter
density and on the Hubble parameter (the cosmic expansion rate). Moreover, the
new measurements agree well with the previous state-of-the-art results that
combined WMAP with the Anglo-Australian 2dF galaxy redshift survey.

"Different galaxies, different instruments, different people and different
analysis -- but the results agree", says Max Tegmark from the University of
Pennsylvania, first author on the two papers. "Extraordinary claims require
extraordinary evidence", Tegmark says, "but we now have extraordinary evidence
for dark matter and dark energy and have to take them seriously no matter how
disturbing they seem."

"The real challenge is now to figure what these mysterious substances actually
are", said another author, David Weinberg from Ohio State University.

SDSS LARGE-SCALE UNDERTAKING

The SDSS is the most ambitious astronomical survey ever undertaken, with more
than 200 astronomers at 13 institutions around the world.

"The SDSS is really two surveys in one", explained Project Scientist James Gunn
of Princeton University. On the most pristine nights, the SDSS uses a wide-field
CCD camera (built by Gunn and his team at Princeton University and Maki
Sekiguchi of the Japan Participation Group) to take pictures of the night sky in
five broad wavebands with the goal of determining the position and absolute
brightness of more than 100 million celestial objects in one-quarter of the
entire sky. When completed, the camera was the largest ever built for
astronomical purposes, gathering data at the rate of 37 gigabytes per hour.

On nights with moonshine or mild cloud cover, the imaging camera is replaced
with a pair of spectrographs (built by Alan Uomoto and his team at The Johns
Hopkins University). They use optical fibers to obtain spectra (and thus
redshifts) of 608 objects at a time. Unlike traditional telescopes in which
nights are parceled out among many astronomers carrying out a range of
scientific programs, the special-purpose 2.5m SDSS telescope at Apache Point
Observatory in New Mexico is devoted solely to this survey, to operate every
clear night for five years.

The first public data release from the SDSS, called DR1, contained about 15
million galaxies, with redshift distance measurements for more than 100,000 of
them. All measurements used in the findings reported here would be part of the
second data release, DR2, which will be made available to the astronomical
community in early 2004.

Strauss said the SDSS is approaching the halfway point in its goal of measuring
one million galaxy and quasar redshifts.

"The real excitement here is that disparate lines of evidence from the cosmic
microwave background (CMB), large-scale structure and other cosmological
observations are all giving us a consistent picture of a Universe dominated by
dark energy and dark matter", said Kevork Abazajian of the Fermi National
Accelerator Laboratory and the Los Alamos National Laboratory.

IMAGE CAPTIONS:

[Image 1:
http://www.sdss.org/news/releases/galaxy_zoom.jpg (265KB)]
The SDSS is two separate surveys in one: galaxies are identified in 2D images
(right), then have their distance determined from their spectrum to create a 2
billion lightyears deep 3D map (left) where each galaxy is shown as a single
point, the color representing the luminosity -- this shows only those 66,976 our
of 205,443 galaxies in the map that lie near the plane of Earth's equator.
(Version without lines, http://www.sdss.org/news/releases/galaxies.jpg)

[Image 2:
http://www.sdss.org/news/releases/fluctuations.jpg (501KB)]
The new SDSS results (black dots) are the most accurate measurements to date of
how the density of the Universe fluctuates from place to place on scales of
millions of lightyears. These and other cosmological measurements agree with the
theoretical prediction (blue curve) for a Universe composed of 5% atoms, 25%
dark matter and 70% dark energy. The larger the scales we average over, the more
uniform the Universe appears. (No frills version,
http://www.sdss.org/news/releases/fl...s_nofrills.jpg)

The authors a

Max Tegmark
Department of Physics, University of Pennsylvania
Philadelphia, PA 19101
Dept. of Physics, Massachusetts Institute of Technology
Cambridge, MA 02139

Michael A. Strauss
Princeton University Observatory
Princeton, NJ 08544

Michael R. Blanton
Center for Cosmology and Particle Physics
Department of Physics, New York University
4 Washington Place
New York, NY 10003

Kevork Abazajian
Theoretical Division, MS B285, Los Alamos National Laboratory
Los Alamos, New Mexico 87545

Scott Dodelson
Center for Cosmological Physics and Department of Astronomy & Astrophysics
The University of Chicago
Chicago, IL 60637;
Fermi National Accelerator Laboratory
P.O. Box 500
Batavia, IL 605107

Havard Sandvik
University of Pennsylvania

Xiaomin Wang
University of Pennsylvania

David H. Weinberg
Department of Astronomy, Ohio State University
Columbus, OH 43210, USA

Idit Zehavi
The University of Chicago

Neta A. Bahcall
Princeton University

Fiona Hoyle
Department of Physics, Drexel University
Philadelphia, PA 19104, USA

David Schlegel
Princeton University

Roman Scoccimarro
New York University

Michael S. Vogeley
Drexel University

Andreas Berlind
The University of Chicago

Tamas Budavari
Department of Physics and Astronomy, The Johns Hopkins University
3701 San Martin Drive, Baltimore, MD 21218

Andrew Connolly
University of Pittsburgh, Department of Physics and Astronomy
3941 O'Hara Street
Pittsburgh, PA 15260

Daniel J. Eisenstein
Department of Astronomy
University of Arizona, Tucson, AZ 85721

Douglas Finkbeiner
Princeton University

Joshua A. Frieman
The University of Chicago; Fermi National Accelerator Laboratory

James E. Gunn
Princeton University

Andrew J. S. Hamilton
JILA and Dept. of Astrophysical and Planetary Sciences
U. Colorado
Boulder, CO 80309

Lam Hui
Fermi National Accelerator Laboratory

Bhuvnesh Jain
University of Pennsylvania

David Johnston
The University of Chicago; Fermi National Accelerator Laboratory

Stephen Kent
Fermi National Accelerator Laboratory

Huan Lin
Fermi National Accelerator Laboratory

Reiko Nakajima
University of Pennsylvania

Robert C. Nichol
Department of Physics, Carnegie Mellon University
5000 Forbes Avenue
Pittsburgh, PA 15213

Adrian Pope
The Johns Hopkins University

Ryan Scranton
University of Pittsburgh

Uros Seljak
Princeton University

Ravi K. Sheth
University of Pittsburgh

Albert Stebbins
Fermi National Accelerator Laboratory

Alexander S. Szalay
The Johns Hopkins University

Istvan Szapudi
Institute for Astronomy, University of Hawaii
2680 Woodlawn Drive
Honolulu, HI 96822

Yongzhong Xu
Theoretical Division, MS B285, Los Alamos National Laboratory
Los Alamos, New Mexico 87545

James Annis
Fermi National Accelerator Laboratory

J. Brinkmann
Apache Point Observatory
2001 Apache Point Rd, Sunspot, NM 88349-0059

Scott Burles
Massachusetts Institute of Technology

Francisco J. Castander
Institut d'Estudis Espacials de Catalunya/CSIC
Gran Capita 2-4, 08034 Barcelona, Spain

Istvan Csabai
The Johns Hopkins University

Jon Loveday
Sussex Astronomy Centre, University of Sussex
Falmer, Brighton BN1 9QJ, UK

Mamoru Doi
Inst. for Cosmic Ray Research, Univ. of Tokyo
Kashiwa 277-8582, Japan

Masataka Fukugita
University of Tokyo

Richard Gott III
Princeton University

Greg Hennessy
U.S. Naval Observatory, Flagstaff Station
Flagstaff, AZ 86002-1149

David W. Hogg
New York University

Zeljko Ivezic
Princeton University

Gillian R. Knapp
Princeton University

Don Q. Lamb
The University of Chicago

Brian C. Lee
Fermi National Accelerator Laboratory

Robert H. Lupton
Princeton University

Timothy A. McKay
Dept. of Physics, Univ. of Michigan
Ann Arbor, MI 48109-1120

Peter Kunszt
The Johns Hopkins University

Jeffrey A. Munn
U.S. Naval Observatory

Liam O'Connell
Sussex Astronomy Centre

Jeremiah P. Ostriker
Princeton University

John Peoples
Fermi National Accelerator Laboratory

Jeffrey R. Pier
U.S. Naval Observatory

Michael Richmond
Physics Dept., Rochester Inst. of Technology
1 Lomb Memorial Dr.
Rochester, NY 14623

Constance Rockosi
The University of Chicago

Donald P. Schneider
Penn State

Christopher Stoughton
Fermi National Accelerator Laboratory

Douglas L. Tucker
Fermi National Accelerator Laboratory

Daniel E. Vanden Berk
University of Pittsburgh

Brian Yanny
Fermi National Accelerator Laboratory

Donald G. York
The University of Chicago, Enrico Fermi Institute
University of Chicago, Chicago, IL 60637