Halo Assembly Bias in the Quasi-linear Regime

Abstract

We address the question of whether or not assembly bias arises in the absence of highly non-linear effects such as tidal stripping of halos near larger mass concentrations. Therefore, we use a simplified dynamical scheme where these effects are not modeled. We choose the punctuated Zel'dovich (PZ) approximation, which prevents orbit mixing by coalescing particles coming within a critical distance of each other. A numerical implementation of this approximation is fast, allowing us to run a large number of simulations to study assembly bias. We measure an assembly bias from 60 PZ simulations, each with 512^3 cold particles in a 128h^-1 Mpc cubic box. The assembly bias estimated from the correlation functions at separations < 5h^-1 Mpc for objects (halos) at z=0 is comparable to that obtained in full N-body simulations. For masses 4x10^11 h^-1 Mo the "oldest" 10% haloes are 3-5 times more correlated than the "youngest" 10%. The bias weakens with increasing mass, also in agreement with full N-body simulations. We find that that halo ages are correlated with the dimensionality of the surrounding linear structures as measured by the parameter (λ_1+λ_2+λ_3)/ (λ_1^2+λ_2^2+λ_3^2)^{1/2} where λ_i are proportional to the eigenvalues of the velocity deformation tensor. Our results suggest that assembly bias may already be encoded in the early stages of the evolution.

7 pages, 5 figures; Minor revision; Accepted for publication in MNRAS

References in corpus (5)

• Assembly bias in the clustering of dark matter haloes
• The dependence of dark halo clustering on the formation epoch and the concentration parameter
• The Dependence of the Mass Assembly History of Cold Dark Matter Halos on Environment
• Environmental Dependence of Cold Dark Matter Halo Formation
• The Clustering of Massive Halos

Cited by in corpus (6)

• On Halo Formation Times and Assembly Bias
• A Halo Model of Galaxy Colors and Clustering in the SDSS
• The assembly bias of dark matter haloes to higher orders
• Environmental dependence in the ellipsoidal collapse model
• Environmental Effects on Real-Space and Redshift-Space Galaxy Clustering
• Non-Gaussian assembly bias from a semi-analytic galaxy formation model