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

Outline

• Superclusters, Shapley

• Superclusters?

• Future of structure in CDM cosmology

• Spherical collapse, gravitational binding

• Redshift-space appearance

• Supercluster boundaries & masses

• Future plans

FF

2MASS Galactic chart2MASS Galactic chart

Shapley Supercluster:Redshift catalog ofProust et al. 2006

Shapley Supercluster:Redshift catalog ofProust et al. 2006

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

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

Pablo A. Araya,PhD Thesis(Groningen), in preparation

Pablo A. Araya, PhD Thesis (Groningen), in preparation

Present(a=1)

Distant future(a=100)

Spherical model• Equation of motion for a mass shell:

• Analytical solution for the “critical” (marginally bound) shell: (Dünner et al. 2006, MNRAS, 366, 803)

Spherical overdensity criterion vs. simulations

28%72%0.26%

Dünner et al. 2006

Radial velocity profile Dünner et al. 2006

Real space vs. redshift space

Dünner et al., submitted (astro-ph/0611435)

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)

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)

The boundaries of Shapley

Dünner et al., in preparation

Supercluster masses

Dünner et al., in preparation

Pablo A. Araya, PhD Thesis (Groningen), in preparation

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.