Interactions between Dark Matter Halos

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Interactions between Dark Matter Halos
Veronika Junk, Andreas Burkert, Elena DOnghia
(University of Munich)

• The Origin of the Hubble Sequence, Vulcano 2005

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Problem Missing Satellites Question,
Overabundance of substructures
on galactic scales with respect to observations,
Suggested Solutions
Astrophysical solutions
Cosmological solutions
(Moore et al. 1999)
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Which role play collisions between substructures ?
Considering penetrating encounters among massive
and less massive subhaloes
Idea when two subhalos collide under a small
enough impact parameter their gaseous
cores will interact and the small core accretes
gas while crossing the large core.
The gas velocity after the collision has to be
compared with the escape velocity of the
massive subhalo,

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• New gas velocity exceeds escape velocity of
  larger halo
• small sat. gains gas whereas big
  sat.
• loses it, if relative velocity
  with respect to the
• small halo is less than its
  escape velocity

Gas will be completly unbound and streams out,
if new gas velocity is larger than escape
velocity of the smaller subhalo and makes it dark
b) New gas velocity is smaller then escape
velocity
Gas of small satellite will remain inside
the massive subhalo making the small one dark,
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Initial setup
Milky Way sized host halo
- Mass
- Virial Radius
- Density profile
Core radius a40 kpc
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Sample of subhaloes
Total number of satellites N300
Mass range
Mass distribution function
Density profile NFW profile
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• Integration of the subhalo orbits over one
  Hubble time
• after each timestep computation of the
  distances between satellites to
• check for an encounter

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Preliminary results and Outlook
Luminous subhalos lie close to observed number
in the Milky Way,
Future
Including more processes, Comparison with
simulations
Comparison with other satellite systems