Evolution of the Halo Mass FunctionZarija Luki (UIUC)Katrin Heitmann (LANL)Salman Habib (LANL)Sergei Bashinsky (LANL)Paul Ricker (UIUC)astro-ph/0702360

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 is the mass variance:2(M) = P(k) W2(k;M) k2 dk0

Why Bothering? At low redshifts (z 2) is used for constraining the dark energy properties (,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!

SimulationsMC2: Particle-Mesh code, tested against other well known cosmo codes (Heitmann et al. 2005, 2007) 2563 DM particles on 10243 grid

Large set of simulations (60) : 1) Different box sizes (4 256 Mpc/h) 2) Many realizations of the same box sizeThat enables us to : 1) Obtain excellent statistics 2) Probe large range of masses (107 1014 h-1 M) and redshifts (0 20).

Visualization 90 Mpchttp://tsoodzil.astro.uiuc/~zlukic/mc2_z=0.mov

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

Results

Universality?

Extended Press-Schechterfbias-ps= fps(c-(R), 2-2(R)) -- Bond et al. 1991

EPS correction

Box-corrected MF

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