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Survival or disruption of CDM micro-haloes: implications for detection experiments

Survival or disruption of CDM micro-haloes: implications for detection experiments. Tobias Goerdt. Collaborators: Oleg Y. Gnedin, Ben Moore, Jürg Diemand and Joachim Stadel. בירושלים העברית האוניברסיטה. Micro-haloes. Cosmological Λ CDM N -body simulations:

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Survival or disruption of CDM micro-haloes: implications for detection experiments

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  1. Survival or disruption of CDM micro-haloes: implications for detection experiments Tobias Goerdt Collaborators: Oleg Y. Gnedin, Ben Moore, Jürg Diemand and Joachim Stadel בירושליםהעבריתהאוניברסיטה

  2. Micro-haloes • Cosmological ΛCDM N-body simulations: • First objects in universe (z ~ 26) • ~1015 in the Milky Way today • Solar system radius • Earth mass Diemand et al. 2005

  3. Dark matter annihilation • Dense cuspy cores • Self-annihilation of DM • Gamma-ray emission • High proper motions (arc-minutes / year) • Uniquely distinguishable • Observable by Glast Koushiappas 2006

  4. Survival issues • Encounters with stars and substructure • Tidal forces in Milky way • Do they get disrupted? • Testing their stability to impulsive gravitational encounters

  5. N-body tests • Equilibrium dark matter halo: • cuspy density profile (α= 1.0, β= 3.0, γ= 1.2) • Mvir = 1 x 10-6 Msun, rvir = 0.01 pc • ~106 particles • Concentration c = 3.2 or c = 1.6 • Perturbing star: • Single particle • M* = 0.7 Msun • 300 km s-1 (solar neighbourhood) • Single and multiple encounters • Varying impact parameters

  6. Numerical results • Density profiles after relaxation • Single encounter • c = 1.6 • Varying impact parameter b • Arrow: rvir

  7. Mass lost • After potential relaxation • Single encounter • c = 1.6 • Varying impact parameter b

  8. Successive encounters: • Density profiles • Multiple encounters • c = 1.6 • Impact parameter: 0.02 pc • Significant fraction unbound • Cuspy central regions remain intact

  9. Cumulative mass loss • Different micro-haloes • Multiple encounters • Impact parameter b = 0.02 pc.

  10. Final masses • Probability density distribution function • Different haloes • Monte Carlo approach • Simulating micro-halo in solar neighbourhood

  11. Annihilation flux • Relative annihilation flux • Both micro-haloes • b = 0.02 pc • Multiple encounters • Mass loss decreases flux of factor of two or three

  12. Summary • Cuspy cores: stable to encounters with disk and halo stars • Mass lost from the outer region • Typical mass loss from a halo decreases flux of a factor of two or three • Still visible in Glast

  13. Any questions?

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