What's new with the Sloan Digital Sky Survey:

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What's new with the Sloan Digital Sky Survey A
project update and some recent results from the
SDSS Presented on behalf of the SDSS by Brian
Yanny Fermilab Jan 31, 2003
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The Sloan Digital Sky Survey (SDSS) is a joint
project of The University of Chicago, Fermilab,
the Institute for Advanced Study, the Japan
Participation Group, The Johns Hopkins
University, the Max-Planck-Institute for
Astronomy (MPIA), the Max-Planck-Institute for
Astrophysics (MPA), New Mexico State University,
Princeton University, Univ of Pittsburgh, the
United States Naval Observatory, and the
University of Washington. Funding for the
project has been provided by the Alfred P. Sloan
Foundation, the Participating Institutions, the
National Aeronautics and Space Administration,
the National Science Foundation, the U.S.
Department of Energy, the Japanese
Monbukagakusho, and the Max Planck Society.
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www.sdss.org
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SDSS related News from the January 2003 American
Astronomical Society Meeting 1. Most distant
known quasar and updated spectra which looks
back to the beginning of the re-ionizzation epoch
at redshifts greater than 6 when the universe was
less than 1 billion years old. 2. New
discoveries regarding stars in our own backyard
and how they will help us to understand the
distribution of dark matterer.
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Fan et al. Highest known redshift quasar z6.4,
when universe was lt 1Gyr old (current age of
universe estimated to be 14 Gyr).
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Spectrum of most distant known quasar (z6.43)
Fan et al 2003.
All flux is absorbed here by Neutral
Hydrogen atoms indicates era of reionization
begins near redshifts of 6.
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Universe goes from ionized to neutral to ionized
Redshift 1000 10 1 0
Redshift What and When
Infinity Big Bang (time
zero) 1500-1000 recombination (BB 300,000
years) 10-20? Early Quasar, Stars(ionization
begins) 6 reionization complete (BB 1
billion yr) 1 Sun and Earth form (BB 9
billion yr) 0 TODAY (BB 14 billion
years)
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Stoughton et al. counts of quasars with redshift
and intrinsic brightness tracks evolution of
massive black holes in the centers of galaxies
since reionization down to the present day.
Redshift (z)
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Ring properties 100 million to half a billion
stars, about the size of the SMC Ten times
thicker than the Galaxys thin disk
INT Data
SDSS Data
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A Disk Galaxy like the Milky Way and its dark
matter halo.
q1.0
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Idit Zehavi, Josh Frieman et al. find in SDSS
projected correlation function a scale at about
1.5 Mpc which may indicate break between single
and multiply occupied dark halos.
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q0.75
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Offcenter or mis-aligned dark haloes are
possible (provided dark matter
is not an illusion)
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Flattened Halo Flattened Disk (centered)
Satellites orbits determined by Halo and Disk
potentials.
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No precession in Spherical potential
q1.0
unreachable in same orbit
In flattened potential, can hit points above

and
below

the
plane
on

side of the Galaxy.
q0.7
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Conclusions 1. Highest known redshift (most
distant) seen at z6.43 (when universe lt 1
billion years old). Probes epoch when hydrogen in
universe was neutral (era of first stars,
galaxies and quasars) 2. A ring of stars
encircling the Milky Way has been detected in
the SDSS. 3. The stellar ring has not been seen
before because it is partially obscured by
foreground stars in the disk of the Milky Way. 4.
Ring may be a companion which was
tidally stretched. 5. Ring of stars is excellent
probe of distribution of dark matter halo
surrounding the Galaxy.