Squeezing the halo bispectrum: a test of bias models

TL;DR

This paper investigates the halo-matter cross bispectrum in the squeezed limit to test different halo bias models, finding that the excursion set peaks model aligns well with simulations, highlighting the importance of scale-dependent bias.

Contribution

It introduces a novel test of halo bias prescriptions using the squeezed limit of the halo bispectrum measured in initial conditions of simulations.

Findings

ESP model agrees well with simulation data

Local bias and peak-background split models often fail

Scale-dependent bias is crucial for accurate bispectrum modeling

Abstract

We study the halo-matter cross bispectrum in the presence of primordial non-Gaussianity of the local type. We restrict ourselves to the squeezed limit, for which the calculation are straightforward, and perform the measurements in the initial conditions of N-body simulations, to mitigate the contamination induced by nonlinear gravitational evolution. Interestingly, the halo-matter cross bispectrum is not trivial even in this simple limit as it is strongly sensitive to the scale-dependence of the quadratic and third-order halo bias. Therefore, it can be used to test biasing prescriptions. We consider three different prescription for halo clustering: excursion set peaks (ESP), local bias and a model in which the halo bias parameters are explicitly derived from a peak-background split. In all cases, the model parameters are fully constrained with statistics other than the cross bispectrum. We measure the cross bispectrum involving one halo fluctuation field and two mass overdensity fields for various halo masses and collapse redshifts. We find that the ESP is in reasonably good agreement with the numerical data, while the other alternatives we consider fail in various cases. This suggests that the scale-dependence of halo bias also is a crucial ingredient to the squeezed limit of the halo bispectrum.