a small part of the via lactea halo

high resolution Milky Way dark matter halos simulated on NASA's Columbia and ORNL's Jaguar supercomputers








VL-2 movies

This movie rotates and zooms into the via lactea-2 halo at z=0 (today). The colors show the local dark matter densities.

VL-1 movies

These animations show the projected dark matter density-square maps of the simulated Milky Way-size halo via lactea-1. The logarithmic color scale covers the same 20 decades in projected density-square in physical units in each frame. All movies are encoded in MPEG format and some are available in different quality versions.

the formation of the via lactea halo

rotation and zoom into the via lactea halo at z=0 (today)
  • slow rotation (large file) : (183 MB)

  • fast rotation (smaller file) : (61 MB)

evolution of the via lactea halo and one of its subhalos since z=2

This movie illustrates the evolution of subhalos by following one example (subhalo #13351). Tidal forces remove most of the mass from this system. During the last pericenter passage it comes within 5.1 kpc of the galactic center, but the inner part of the subhalo is still able to survive (even mass beyond the tidal radius at pericenter remains bound to the subhalo, see astro-ph/0703337).

Also note how the subhalo becomes rounder during tidal mass loss, and how its major axis points roughly towards the galactic center most of the time, see astro-ph/0705.2037.

halo and  subhalo evolution
  • high resolution (large file) : (181 MB)     reduced resolution (smaller file) : (37 MB)

  • the inset shows only particles within a 20 kpc cube centered on subhalo #13351
  • the inset also shows projected dark matter density-square but using a different color map to highlight shape and orientation
  • the red box in the main panel shows the position and size of the inset
  • the red circle indicates the direction and 3D distance to the center (170 kpc at z=2)
  • the history of subhalo #13351 is plotted in cyan in Figures 12 and 13 of astro-ph/0703337
  • its shape and orientation is plotted in upper right panel of Figure 11 in astro-ph/0705.2037
halo and subhalo evolution
  • animated 3D orbit plot for subhalo #13351: (11 MB)

  • track starts at z=2 (in the lower central region of the plot) and ends at z=0 (lower right)
  • these orbits are not confined to planes since the host potential is not spherical
  • for more examples see Figure 10 of astro-ph/0705.2037

infall caustics in dark matter halos?

The following two movies show the mass accretion and halo structure of via lactea in the radial velocity - radius plane. They are animated versions of figures 1 and 2 in astro-ph/0804.4185.

accretion of subhalos plotted in the radial velocity - radius plane phase space distribution of subhalos
  • mpeg movie (24 MB)
  • the upper left panel shows all subhalos. In the other panels they are separated by the number of orbits they have completed.
  • individual subhalos move clockwise in the full plot (upper left panel).
  • branch patterns, each one corresponding to a certain number of orbits, move from left to right.
  • "caustics" occur on these branches at the points of small radial velocity.
  • symbols illustrate the orbits of six subhalos, which form part of the 3rd "caustic" at the end.
accretion of particles plotted in the radial velocity - radius plane phase space distribution of dark matter particles
  • mpeg movie (21 MB)
  • main panel: particle distribution. The straight line is the caustic velocity.
  • lower panel: mass profiles of all particles (black) and of a subset within 24 km/s of the caustic velocity (red).

last updated: August 6, 2008, by J. Diemand

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