Dependence of halo bias on mass and environment

TL;DR

This paper investigates how halo bias depends on both mass and environment, revealing that environment plays a dominant role in halo clustering when fixed, which impacts cosmological and galaxy formation studies.

Contribution

It demonstrates that halo clustering is primarily determined by environment rather than mass when the large-scale environment is held constant, providing a new framework for understanding halo and galaxy correlations.

Findings

Halo bias is mainly environment-dependent at fixed large-scale environment.

Mass alone is insufficient to predict halo clustering.

Environmental correlations influence galaxy property correlations.

Abstract

The simplest analyses of halo bias assume that halo mass alone determines halo clustering. However, if the large scale environment is fixed, then halo clustering is almost entirely determined by environment, and is almost completely independent of halo mass. We show why. Our analysis is useful for studies which use the environmental dependence of clustering to constrain cosmological and galaxy formation models. It also shows why many correlations between galaxy properties and environment are merely consequences of the underlying correlations between halos and their environments, and provides a framework for quantifying such inherited correlations.