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

Micro-haloes Cosmological ΛCDM N-body simulations: –First objects in universe (z ~ 26) –~10 15 in the Milky Way today –Solar system radius –Earth mass Diemand et al. 2005

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

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

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

Numerical results Density profiles after relaxation Single encounter c = 1.6 Varying impact parameter b Arrow: r vir

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

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

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

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

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

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

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