Cold Dark Matter (WIMPs)

Warm Dark Matter (mostly CDM but with some neutrinos as well)

Hot Dark Matter (neutrinos)

Simulations by Ben Moore (Univ. of Zurich)

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)

Galaxies are observed to be “clustered” in space (not random)

Which one is the 2dFGRS? Which are taken from CDM simulations?

P(k) from SDSS

From Tegmark et al. (2004)

Galaxy Power Spectrum from SDSS (data points) compared to Lambda-CDM prediction (red line)

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/

Zoom in to a cluster at z=0

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

AREPO: newest 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)