1. Evolution of the Halo Mass Function Zarija Lukić (UIUC) Katrin Heitmann (LANL) Salman Habib (LANL) Sergei Bashinsky (LANL) Paul Ricker (UIUC) astro-ph/0702360

2. Mass function - Distribution of masses in the Universe: bin all objects (halos) in mass bins – dn/dM - Or, presenting it in a redshift (+cosmology) independent way : where σ is the mass variance: σ 2 (M) = P(k) W 2 (k;M) k 2 dk ∫ ∞ 0

3. Why Bothering? - At low redshifts (z ≤ 2) is used for constraining the dark energy properties (Ω λ,w) - At high redshift is used for quasar abundances & formation sites, reionization history and first stars studies - At high redshift (2006) data from different groups differ by a factor of few!

4. Simulations -MC 2 : Particle-Mesh code, tested against other well known cosmo codes (Heitmann et al. 2005, 2007) - 256 3 DM particles on 1024 3 grid -Large set of simulations (60) : 1) Different box sizes (4 – 256 Mpc/h) 2) Many realizations of the same box size -That enables us to : 1) Obtain excellent statistics 2) Probe large range of masses (10 7 – 10 14 h -1 M ☼ ) and redshifts (0 – 20).

5. Visualization – 90 Mpc http://tsoodzil.astro.uiuc/~zlukic/mc2_z=0.mov

6. FOF mass correction N corr = N (1-N -0.6 ) (Warren et al.2006) - Very important for interpreting data!

7. Results

8. Universality?

9. Extended Press-Schechter ∞∞ f bias-ps = f ps (δ c -δ(R), σ 2 -σ 2 (R)) -- Bond et al. 1991

10. EPS correction

11. Box-corrected MF

12. Corollary - Need FOF number of particles correction, and to account for finite box correction, especially for high z - Warren et al. fit gives prediction with 10% accuracy for a wide range of masses and redshifts (ST very good as well) - Good evidence for the universality in CDM phase (z ≥ 5) - Possible breaking of universality with entrance of dark energy? - For more check: astro-ph/0702360