Non-Gaussian Halo Mass Function and Non-Spherical Halo Collapse: Theory vs. Simulations

Details Non-Gaussian Halo Mass Function and Non-Spherical Halo Collapse: Theory vs. Simulations Non-Gaussian Halo Mass Function and Non-Spherical Halo Collapse: Theory vs. Simulations

2011-09-14

arxiv.org/abs/1109.3196v2

JCAP 02 (2012) 002

Astronomy and Astrophysics

Astrophysics

Cosmology and Extragalactic Astrophysics

29 pages, 9 figures, typos corrected and added clarifications on the barrier model. Matches JCAP submitted version

Scientific paper

10.1088/1475-7516/2012/02/002

The mass distribution of dark matter halos is a sensitive probe of primordial non-Gaussianity (NG). We derive an analytical formula of the halo mass function by perturbatively computing excursion set path-integrals for a non-Gaussian density field with non-vanishing skewness, fnl. We assume a stochastic barrier model which captures the main features of the ellipsoidal collapse of halos. Contrary to previous results based on extensions of the Press-Schechter formalism to NG initial conditions, we find that the non-spherical collapse of halos directly alter the signature of primordial NG. This points toward a potential degeneracy between the effect of primordial non-Gaussianity and that of non-linear halo collapse. The inferred mass function is found to be in remarkable agreement with N-body simulations of NG local type. Deviations are well within numerical uncertainties for all values of fnl^loc in the range of validity of the perturbative calculation (|fnl^loc|< 200). Moreover, the comparison with simulation results suggests that for |fnl^loc|> 30 the non-linear collapse of halos, as described by our barrier model, strongly deviates from that of Gaussian initial conditions. This is not surprising since the effect of non-linear gravitational processes may be altered by initially large NG. Hence, in the lack of prior theoretical knowledge, halo collapse model parameters should be included in statistical halo mass function data analysis which aim to constrain the signature of primordial NG

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