A new method to measure galaxy bias

TL;DR

This paper introduces a novel method for modeling galaxy bias using full non-linear information from matter density moments, revealing significant differences from traditional approaches and questioning the adequacy of second-order local Eulerian bias models.

Contribution

The paper develops a new approach leveraging non-linear moments of the matter density field and tests the validity of second-order Eulerian bias, providing more accurate bias parameter constraints.

Findings

Full non-linear information yields different bias parameters than perturbation theory.

Neglecting non-linear details biases results in the studied scale range.

Second-order Eulerian bias scheme shows inconsistencies and may be too simplistic.

Abstract

We present a new approach for modelling galaxy/halo bias that utilizes the full non-linear information contained in the moments of the matter density field, which we derive using a set of numerical simulations. Although our method is general, we perform a case study based on the local Eulerian bias scheme truncated to second-order. Using 200 N-body simulations covering a total comoving volume of 675 (Gpc/h)^3, we measure several 2- and 3-point statistics of the halo distribution to unprecedented accuracy. We use the bias model to fit the halo-halo power spectrum, the halo-matter cross spectrum and the corresponding three bispectra for wavenumbers in the range 0.04 < k < 0.12 h Mpc^-1. We find the constraints on the bias parameters obtained using the full non-linear information differ significantly from those derived using standard perturbation theory at leading order. Hence, neglecting the full non-linear information leads to biased results for this particular scale range. We also test the validity of the second-order Eulerian local biasing scheme by comparing the parameter constraints derived from different statistics. Analysis of the halo-matter cross-correlation coefficients defined for the 2- and 3-point statistics reveals further inconsistencies contained in the second-order Eulerian bias scheme, suggesting it is too simple a model to describe halo bias with high accuracy.