Superclusters as future “island universes” – the case of Shapley
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Superclusters as future “island universes” –
the case of Shapley
Andreas Reisenegger
PUC / ESO
Theory/simulations:Rolando Dünner (PUC)Andrés Meza (UChile/UNAB)Pablo A. Araya (Groningen)
Observations:Hernán Quintana (PUC)Dominique Proust (Meudon)E. Rodrigo Carrasco (Gemini)+ several others
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Outline
• Superclusters, Shapley
• Superclusters?
• Future of structure in CDM cosmology
• Spherical collapse, gravitational binding
• Redshift-space appearance
• Supercluster boundaries & masses
• Future plans
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FF
2MASS Galactic chart2MASS Galactic chart
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Shapley Supercluster:Redshift catalog ofProust et al. 2006
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Shapley Supercluster:Redshift catalog ofProust et al. 2006
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Superclusters?
• What is a supercluster?• What are its boundaries?
So far, definitions have been– Vague: agglomeration of galaxies or clusters, or– Arbitrary: some overdensity, or– Very technical: largest non-percolating structures.
– NOT physical
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CDM Cosmology• Initially matter-dominated:
– hierarchical growth of structure
– up to clusters of galaxies (so far)
• Now, is taking over:
– expansion accelerates! (supernovae)
– bound structures separate from each other
– structure formation stops
Some structures are dense enough to locally dominate over , but not yet virialized
– will collapse within the next Hubble time or so
– largest bound structures in the Universe
– physical definition of superclusters
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Pablo A. Araya,PhD Thesis(Groningen), in preparation
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Pablo A. Araya, PhD Thesis (Groningen), in preparation
Present(a=1)
Distant future(a=100)
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Spherical model• Equation of motion for a mass shell:
• Analytical solution for the “critical” (marginally bound) shell: (Dünner et al. 2006, MNRAS, 366, 803)
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Spherical overdensity criterion vs. simulations
28%72%0.26%
Dünner et al. 2006
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Radial velocity profile Dünner et al. 2006
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Real space vs. redshift space
Dünner et al., submitted (astro-ph/0611435)
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Bound structures in redshift space
Velocity envelopes derived through spherical collapse from density profiles of simulated structures
Dünner et al., submitted (astro-ph/0611435)
Radial velocity from:•true density profile (solid)•NFW density profile (dashed)•simulation (dots: bound=green, unbound=blue)
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Redshift-space
boundary
• Shape is velocity envelope from:– True density profile (black, solid)
– NFW profile + spherical collapse (dashed, red & green)
• Calibrate redshift-space density through simulations to be able to fit to observed data
Dünner et al., submitted (astro-ph/0611435)
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The boundaries of Shapley
Dünner et al., in preparation
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Supercluster masses
Dünner et al., in preparation
Pablo A. Araya, PhD Thesis (Groningen), in preparation
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Near future
• Verify spherical collapse model through Dn- distances to individual clusters in Shapley (Magellan proposal: Quintana, Reisenegger, Melnick, Selman, ...).
• Claimed disagreement of predicted vs. observed supercluster mass function (Einasto et al. 2006): verify through redshift-space analysis of simulations vs. SDSS or 2dFGRS.
• Improve & compare mass determination methods in simulations & in Shapley.
• Center for the Exploration of Superclusters of Galaxies (CESGA): “Milenio” proposal, in 2nd round of evaluation.