Evolution of the Halo Mass Function

Zarija Lukić (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 σ is the mass variance:

σ2(M) = P(k) W2(k;M) k2 dk∫∞

0

Why Bothering?

- At low redshifts (z ≤ 2) is used for constraining the dark energy properties (Ωλ,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!

Simulations

- MC2: 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 size- That 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 correction

Ncorr = N (1-N-0.6)

(Warren et al.2006)

- Very important for interpreting data!

Results

Universality?

Extended Press-Schechter

∞ ∞

fbias-ps= fps(δc-δ(R), σ2-σ2(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