Halo mass function and scale-dependent bias from N-body simulations with non-Gaussian initial conditions: Halo-clustering and early non-Gaussianity

Abstract

We perform a series of high-resolution N-body simulations of cosmological structure formation starting from Gaussian and non-Gaussian initial conditions. We adopt the best-fitting cosmological parameters from the third- and fifth-year data releases of the Wilkinson Microwave Anisotropy Probe, and we consider non-Gaussianity of the local type parametrized by eight different values of the non-linearity parameter fNL. Building upon previous work based on the Gaussian case, we show that, when expressed in terms of suitable variables, the mass function of friends-of-friends haloes is approximately universal (i.e. independent of redshift, cosmology and matter transfer function) to good precision (nearly 10 per cent) also in non-Gaussian scenarios. We provide fitting formulae for the high-mass end (M > 1013h−1 M⊙) of the universal mass function in terms of fNL, and we also present a non-universal fit in terms of both fNL and z to be used for applications requiring higher accuracy. For Gaussian initial conditions, we extend our fit to a wider range of halo masses (M > 2.4 × 1010h−1 M⊙) and we also provide a consistent fit of the linear halo bias. We show that, for realistic values of fNL, the matter power spectrum in non-Gaussian cosmologies departs from the Gaussian 1 by up to 2 per cent on the scales where the baryonic-oscillation features are imprinted on the two-point statistics. Finally, using both the halo power spectrum and the halo-matter cross spectrum, we confirm the strong k-dependence of the halo bias on large scales (k < 0.05 h Mpc−1) which was already detected in previous studies. However, we find that commonly used parametrizations based on the peak-background split do not provide an accurate description of our simulations which present extra dependencies on the wavenumber, the non-linearity parameter and, possibly, the clustering strength. We provide an accurate fit of the simulation data that can be used as a benchmark for future determinations of fNL with galaxy surveys.