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

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

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

4. 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.

5. Superclusters Not spherical, not virialized
Filamentary = long “chains” of clusters and galaxies (possibly weak “bridge” of galaxies connects superclusters)
All “rich” clusters are members of superclusters
220 known superclusters
Typical separations between superclusters: 100 h-1 Mpc
Lengths are as much as 100h-1Mpc
Superclusters surround ”voids”

6. Voids
Roughly spherical; typical radius is 40h-1 Mpc (more than 40x the radius of the Local Group)
Regions of exceptionally low galaxy density (smallest voids may be truly “empty” of galaxies)
Do not contain “bright” galaxies (i.e., L*or brighter)
Not filled with ultra-faint dwarf galaxies (would have been found by deep HI surveys)
Not filled with dark matter (matter density is approximately equal to the galaxy density in voids, based on simulations)
Region of space where galaxy formation was retarded/slowed rather than completely failed
Regions of space that are expanding FASTER than the average rate in the universe

7. “Fly Through” of Sloan Digital Sky Survey Data Release 9 (DR9)
Note the 3-d nature of the structure in the galaxies
Note the abundance of groups/clusters and voids
Note the “supercluster” just before the end
Available at:

8. CDM Simulation (red = galaxy cluster location)

9. Luminosity Segregation

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

11. 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

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

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

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

15. 2dFGRS zcones vs. CDM

16. 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

17. 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

18. Two “Dark Matter Only” Movies from Millennium Run Simulation:
“Zoom in” on a galaxy cluster at z = 0
Growth of structure in “co-moving coordinates” from z =20 to z = 0

19. Zoom in to a cluster at z=0

20. Growth of structure from z=20 to z=0 in “comoving” coordinates

21. AREPO: new DM+hydro galaxy formation code
Mark Vogelsberger, Debora Sijacki, Dusan Keres, Volker Springel, and Lars Hernquist (2011/2012)
Trying to do real “galaxy formation” in a large volume (but only 203 h-3 Mpc3) with very high force resolution (smoothing length of 1 kpc in some cases)
Major improvement is in treatment of gas, not dark matter
Highest-resolution simulation has 5123 dark matter particles (mp = 3.7x106 Msun), 5123 gas particles (mp=7.4x105 Msun)
First time for formation of “realistic” spirals and modeling of galaxy interactions in a “large” volume of the universe
Too small to count as a “cosmological” volume, but going in the direction we need

22. Zoom-in on a z=1 galaxy from AREPO (gas density)

23. Illustris Project http://www.illustris-project.org
Mark Vogelsberger, Volker Springel, Debra Sijacki, Greg Snyder, Dylan Nelson, Shy Genel, Paul Torrey, Dandan Xu, Simeon Bird, Lars Hernquist
Set of large-scale cosmological simulations, including the most ambitious numerical simulation of galaxy formation done to date (uses AREPO code)
Six simulations (three are “cold dark matter only”), same size volume in all cases (Volume = Mpc3) but with varying force and mass resolution, evolved from z = 127 to z = 0
Highest resolution simulation has dark matter particles of mass 6.3x106 Msun, gas particles (initially) of mass 1.6x106 Msun, force resolution of 0.7 kpc for baryons and 1.4 kpc for dark matter (can “resolve” galaxies that are as small as 109 Msun in luminous material (stars, cold gas, hot gas)
All completely public (released in 2015) and easy to use! But, to store a “full slice” (= all particles at a given redshift) you need ~2.5TB of disk space.
Some of the most realistic numerical galaxies simulated to date (but not perfect match to observed galaxies)

24. Illustris Hubble Sequence of Galaxies at z = 0

25. HST Ultra Deep Field (left) vs. Illustris “Deep Field” (right)

26. 103 Mpc3 region of Illustris Left: Cold Dark Matter Density, Right: Gas Temperature

27. Full Illustris Volume Left: Cold Dark Matter Density, Right: Gas Temperature
Movie starts from z = 15