1. Core of Coma Cluster (optical)

2. Coma Cluster (X-ray + optical)
X-ray gas shows “substructure” (big surprise when it was discovered)

3. A2218

4. 500,000 statistically-random dots

5. Brightest ~500,000 Galaxies in the Northern Hemisphere (1977; RA & DEC only)
2-D “lacework” pattern

6. CfA “Slice of the Universe” (1987; first 3-D view of the galaxy distribution)

7. Two Degree Field Galaxy Redshift Survey (2dFGRS); ~250,000 galaxies

8. Blow-up of a region of the 2dF pie slice

9. The Local Network of “Superclusters” and Voids (organization of the universe on the largest scale)
Galaxies cluster together to form “groups” or “clusters” of galaxies
Clusters of galaxies cluster together to form “superclusters” of galaxies
Superclusters are still in the process of forming (not virialized)
We belong to the Virgo Supercluster
Voids are regions of space where, for some reason, galaxies had a hard time forming
Each white dot in the picture represents a galaxy.

11. CDM Simulation (red = galaxy cluster location)

12. Luminosity Segregation

13. Cold, Warm & Hot Dark Matter Universes
CDM
Dark matter only simulations by Ben Moore (University of Zurich)
WDM
HDM

14. CDM generically predicts mildly-flattened halos (<e> ~ 0
CDM generically predicts mildly-flattened halos (<e> ~ 0.3) with a lot of dark matter substructure
Spherically-averaged density profile is NOT isothermal (it’s called the “Navarro, Frenk & White” density profile)
Milky Way sized halo from one of Ben Moore’s simulations

15. One of these is the actual Coma cluster; one is a dark matter simulation of a cluster by Ben Moore

16. CDM generically gives “filamentary” structure in the universe (another of Ben Moore’s simulations)

17. Two Degree Field Galaxy Redshift Survey (2dFGRS); ~250,000 galaxies

18. 2dFGRS zcones vs. CDM

19. P(k) from SDSS
Galaxy Power Spectrum from SDSS (data points) compared to Lambda-CDM prediction (red line)
From Tegmark et al. (2004)
The “power spectrum” is the Fourier transform of the two-point correlation function

20. Millennium Run Simulation (Volker Springel et al. 2005)
At the time it was the largest CDM simulation ever run (> 10 billion particles)
mp = 8.6 x 108 Msun
500 h-1 Mpc x 500 h-1 Mpc x 500 h-1 Mpc box
Force resolution of 5 kpc
More than 20 million galaxies
Much of the data are publicly-available
Movies available at

21. Zoom in to a cluster at z=0