Clusters and superclusters in the Sloan Digital Sky Survey

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Clusters and superclusters in the Sloan Digital
Sky Survey

• Jaan Einasto
• Tartu Observatory
• July 2003

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Summary

• Overview of recent surveys
• Las Campanas Redshift Survey
• Sloan Digital Sky Survey
• Distant supernova project
• 2. Clusters and superclusters in the Sloan Survey

• Density field of SDSS and LCRS, Density field
  clusters and superclusters
• Luminosity function of DF-clusters
• Galaxies and clusters in different environment
• Distribution of early and late type galaxies

• Comparison with distant supernova and CMB data
• Conclusions
• In collaboration with Maret Einasto, E. Saar, G.
  Hütsi,
• E. Tago, V. Mueller, D. Tucker

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Las Campanas Redshift Survey

• 1990 2000 25000 redshifts in 6 strips,
• -3, -6, -12 in the Northern sky
• -39, -42, -45 in the Southern sky
• Main results
• Galaxy and cluster (group) map
• Correlation function and power spectrum
• 3. Void analysis
• Possible presence of a scale 100 Mpc/h

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Distribution of Abell clusters (white) and X-ray
clusters (red)
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Abell clusters (red) and LCRS clusters (blue).
Global structure Better visible using 3-D Abell
cluster data
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Sloan Digital Sky Survey
1995 2005 Special 2.5-m telescope Digital
scanning of Northern Sky in 5 colours 100
million galaxies, quasars and stars Spectroscopy
(redshifts rlt17.7, SED types) 1 million
galaxies, 100000 quasars
Early Data Release (2001) 35.000 redshifts in
2 strips along celestial equator Data Release 1
(2003) 130.000 redshift in several
strips Data collection finished (expectation)
2005
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Data and density field

• Early Data Release (25000 galaxies in equatorial
  strip)
• Data Release 1 (30000 galaxies in equatorial
  strip)
• LCRS (25000 galaxies in 6 strips, loose groups)
• Abell clusters and superclusters

• Density field is found in steps
• Calculate galaxy absolute magnitude
• Find total magnitude correction for faint
  galaxies (Schechter)
• Define density field with 1 Mpc/h cell size
• Smooth density with 0.8 Mpc/h and 10 Mpc/h Gauss
  kernel

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Number density (gray) and luminous density
(black) weights Observed luminosities
(grey) and total luminosities (black) corrected
for unobserved galaxies outside the
observational window
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Density field clusters and superclusters
DF-cluster found as density peaks of the
high-resolution field. DF-superclusters large
overdensity regions in the low-resolution
field. Density of the low-resolution density
field is used as the parameter to characterize
the environment of DF-clusters
Selection effect
Total luminosity of DF-clusters as a function of
distance. Low-luminous clusters on large
distances are not visible(contain no bright
galaxies within the observational
window).Statistically they can be restored in
calculation luminosity function
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Luminosity function of DF-clusters

• Luminosity function of SDSS DF-clusters for
  various environment density (left). Note the
  difference of high luminosity end for
• different environmental density
• Luminosity function of LCRS DF-clusters (right)

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Galaxies and clusters in different environment
The luminosity of galaxies (left) and DF-clusters
(right) as a function of the density of the
environment. In low-density regions most luminous
galaxies and clusters are 10 times less
luminous than in high-density regions
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Cluster mass N in numerical experiments at
different environment density d In low-density
regions most massive clusters are 100 times less
massive than in high-density environment
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Density field for early and late type galaxies

• Using color index early
• and late type galaxies can be separated.
• Upper figure density field for early galaxies
• Lower figure for late galaxies. There are more
  late type galaxies in low-density regions

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Distribution of early (top) and late (bottom)
type galaxies in SDSS Northern equatorial
strip. Dark blue galaxies in low-den
environment Red galaxies in high-den
environment
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Superclusters with Abell clusters
Luminosity of superclusters as a function of the
richness (the number of DF-clusters). Filled
circles - superclusters with Abell
clusters Open circles superclusters without
Abell clusters Abell superclusters are richer
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Conclusions

• SDSS and LCRS data have been used to calculate
  high- and low-resolution density field and find
  DF-clusters and superclusters
• Galaxies and clusters in superclusters
  (high-density regions) are up to 10 times more
  luminous than in low-density regions
• Superclusters with Abell clusters are richer
  environmental enrichment is important on
  supercluster scales
• Early type galaxies are more concentrated to
  superclusters than late type galaxies. Late type
  galaxies dominate in low-density regions.
• Cosmological parameters are known with high
  accuracy
• the Universe is accelerating