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    A Map of the Universe from Sloan Digital Sky Survey
    Oleh : Suharyo S.
    Selasa, 28 Oktober 2003 (17:54 WIB) dari IP

    Paper: astro-ph/0310571
    From: Richard Gott III
    Date: Mon, 20 Oct 2003 18:36:03 GMT (2264kb)

    Title: A Map of the Universe
    Authors: J. Richard Gott III, Mario Juri\'c, David Schlegel, Fiona Hoyle,
    Michael Vogeley, Max Tegmark, Neta Bahcall, Jon Brinkmann
    Comments: Additional material accessible on the web at:
    We have produced a new conformal map of the universe illustrating recent
    discoveries, ranging from Kuiper belt objects in the Solar system, to the
    galaxies and quasars from the Sloan Digital Sky Survey. This map projection,
    based on the logarithm map of the complex plane, preserves shapes locally, and
    yet is able to display the entire range of astronomical scales from the Earth's
    neighborhood to the cosmic microwave background. The conformal nature of the
    projection, preserving shapes locally, may be of particular use for analyzing
    large scale structure. Prominent in the map is a Sloan Great Wall of galaxies
    1.37 billion light years long, 80onger than the Great Wall discovered by
    Geller and Huchra and therefore the largest observed structure in the universe.
    \\ ( , 1830kb)

    3D Map of Universe Bolsters Case for Dark Energy and Dark Matter
    Oleh : Suharyo S.
    Jumat, 31 Oktober 2003 (18:18 WIB) dari IP

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

    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 -- 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,, on October 28.
    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


    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. (Click for high resolution jpg, version without lines.)

    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.
    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


    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, 25ark matter and 70ark energy. The larger the scales we average
    over, the more uniform the Universe appears. (Click for high resolution jpg,
    no frills version.)

    "The real challenge is now to figure what these mysterious substances
    actually are", said another author, David Weinberg from Ohio State
    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.
    The authors are:
    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
    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
    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
    Stephen Kent, Fermi National Accelerator Laboratory
    Huan Lin, Fermi National Accelerator Laboratory
    Reiko Nakajima, University of Pennsylvania
    Robert C. Nichol, Department of Physics, 5000 Forbes Avenue, Carnegie
    Mellon University, 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
    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

    Send Web-related comments and questions to

    Re: A Map of the Universe from Sloan Digital Sky Survey
    Oleh : Nur Baidha
    Selasa, 9 Desember 2003 (00:57 WIB) dari IP



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