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

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

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

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.

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”

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

“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: http://www.sdss3.org/press/movies/dr9miguel_1080.mov

CDM Simulation (red = galaxy cluster location)

Luminosity Segregation

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

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

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

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

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

2dFGRS zcones vs. CDM

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

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 http://www.mpa-garching.mpg.de/galform/virgo/millennium/

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

Zoom in to a cluster at z=0

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

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

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

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 = 106.53 Mpc3) but with varying force and mass resolution, evolved from z = 127 to z = 0 Highest resolution simulation has 18203 dark matter particles of mass 6.3x106 Msun, 18203 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)

Illustris Hubble Sequence of Galaxies at z = 0

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

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

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