Evolution of the Halo Mass Function Zarija Lukić (UIUC) Katrin Heitmann (LANL) Salman Habib (LANL)...

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