N-body simulations with generic non-Gaussian initial conditions I: Power Spectrum and halo mass function

TL;DR

This paper develops a flexible method for generating non-Gaussian initial conditions in N-body simulations, tests it with inflationary shapes, and compares the results to existing theoretical models for the power spectrum and halo mass function.

Contribution

It introduces a general approach to create non-Gaussian initial conditions for any bispectrum shape, applicable to inflationary models, and validates the method through simulations matching theoretical predictions.

Findings

Halo mass function matches analytical models

Non-linear power spectrum agrees with literature

Method works for various inflationary non-Gaussian shapes

Abstract

We address the issue of setting up generic non-Gaussian initial conditions for N-body simulations. We consider inflationary-motivated primordial non-Gaussianity where the perturbations in the Bardeen potential are given by a dominant Gaussian part plus a non-Gaussian part specified by its bispectrum. The approach we explore here is suitable for any bispectrum, i.e. it does not have to be of the so-called separable or factorizable form. The procedure of generating a non-Gaussian field with a given bispectrum (and a given power spectrum for the Gaussian component) is not univocal, and care must be taken so that higher-order corrections do not leave a too large signature on the power spectrum. This is so far a limiting factor of our approach. We then run N-body simulations for the most popular inflationary-motivated non-Gaussian shapes. The halo mass function and the non-linear power spectrum agree with theoretical analytical approximations proposed in the literature, even if they were so far developed and tested only for a particular shape (the local one). We plan to make the simulations outputs available to the community via the non-Gaussian simulations comparison project web site http://icc.ub.edu/~liciaverde/NGSCP.html.