Abundance of peaks and dips in three-dimensional mass and halo density fields: a test for cosmology

TL;DR

This study uses cosmological simulations to analyze the abundance of peaks and dips in 3D mass and halo density fields, revealing their potential as probes for cosmological parameters and primordial non-Gaussianity.

Contribution

It demonstrates that the abundance of density extrema is well described by existing models and varies with non-Gaussian initial conditions, offering a new method to test cosmology.

Findings

Peak abundance matches Gaussian predictions across conditions.

Height distribution fits a log-normal on quasi-linear scales.

Non-Gaussian models show distinct extrema abundance patterns.

Abstract

Using cosmological N-body simulations, we study the abundance of local maxima (peaks) and minima (dips) identified in the smoothed distribution of halos and dark matter (DM) on scales of $10-100$s Mpcs. The simulations include Gaussian and local-type $f_{\rm NL}$ non-Gaussian initial conditions. The expression derived in the literature for the abundance (irrespective of height) of peaks for Gaussian fields is surprisingly accurate for the evolved halo and DM density fields for all initial conditions considered. Furthermore, the height distribution is very well fitted by a log-normal on quasi-linear scales. The abundance as a function of scale depends on the cosmological parameters ($H_0$ and background matter densities) through the shape of the power spectrum, but it is insensitive to the clustering amplitude. Further, the abundance in the smoothed halo distribution is substantially different in the non-Gaussian from the Gaussian simulations. The interpretation of this effect is straightforward in terms of the scale dependence of halo bias in non-Gaussian models. The abundance of extrema extracted from three-dimensional large galaxy redshift surveys could be a competitive probe of the cosmological parameters and initial non-Gaussianity. It breaks the degeneracy between $f_{\rm NL}$ and the clustering amplitude, making it complementary to counts of galaxy clusters and peaks in weak-lensing maps.