The Effect of Local non-Gaussianity on the Matter Bispectrum at Small Scales

TL;DR

This paper models the matter bispectrum considering local primordial non-Gaussianity across small scales using the Halo Model, providing predictions that extend beyond current simulation capabilities.

Contribution

It introduces a Halo Model approach incorporating non-Gaussian corrections to predict the matter bispectrum at small scales, validated against simulations.

Findings

Deviations between Halo Model and simulations are under 10% in the squeezed limit.

Non-Gaussian initial conditions with fNL=100 enhance the bispectrum by 15-25% at small scales.

Provides a simple formula for quick bispectrum evaluation in various scenarios.

Abstract

We compute the matter bispectrum in the presence of primordial local non-Gaussianity over a wide range of scales, including the very small nonlinear ones. We use the Halo Model approach, considering non-Gaussian corrections to the halo profiles, the halo mass function and the bias functions. We compare our results in the linear and mildly nonlinear scales to a large ensemble of Gaussian and non-Gaussian numerical simulations. We consider both squeezed and equilateral configurations, at redshift z = 0 and z = 1. For z = 0, the deviations between the Halo Model and the simulations are smaller than 10% in the squeezed limit, both in the Gaussian and non-Gaussian cases. The Halo Model allows to make predictions on scales much smaller than those reached by numerical simulations. For local non-Gaussian initial conditions with a parameter fNL = 100, we find an enhancement of the bispectrum in the squeezed configuration k = k3 = k2 >> k1 \sim 0.01 h^{-1} Mpc, of \sim 15% and \sim 25% on scales k \sim 1 h^{-1} Mpc, at z = 0 and z = 1 respectively. This is mainly due to the non-Gaussian corrections in the linear bias. Finally we provide a very simple expression valid for any scenario, i.e. for any choice of the halo profile, mass and bias functions, which allow for a fast evaluation of the bispectrum on squeezed configurations.