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Halo assembly bias and the tidal anisotropy of the local halo environment

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TLDR
In this article, the role of the local tidal environment in determining the assembly bias of dark matter haloes was studied, using correlations between the large-scale and small-scale environments of simulated haloes at z = 0 with masses between 10^11.6 and 10^14.9.
Abstract
We study the role of the local tidal environment in determining the assembly bias of dark matter haloes. Previous results suggest that the anisotropy of a halo's environment (i.e. whether it lies in a filament or in a more isotropic region) can play a significant role in determining the eventual mass and age of the halo. We statistically isolate this effect, using correlations between the large-scale and small-scale environments of simulated haloes at z = 0 with masses between 10^11.6 ≲ (m/h^−1 M_⊙) ≲ 10^14.9. We probe the large-scale environment, using a novel halo-by-halo estimator of linear bias. For the small-scale environment, we identify a variable α_R that captures the tidal anisotropy in a region of radius R = 4R_200b around the halo and correlates strongly with halo bias at fixed mass. Segregating haloes by α_R reveals two distinct populations. Haloes in highly isotropic local environments (α_R ≲ 0.2) behave as expected from the simplest, spherically averaged analytical models of structure formation, showing a negative correlation between their concentration and large-scale bias at all masses. In contrast, haloes in anisotropic, filament-like environments (α_R ≳ 0.5) tend to show a positive correlation between bias and concentration at any mass. Our multiscale analysis cleanly demonstrates how the overall assembly bias trend across halo mass emerges as an average over these different halo populations, and provides valuable insights towards building analytical models that correctly incorporate assembly bias. We also discuss potential implications for the nature and detectability of galaxy assembly bias.

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Citations
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Journal ArticleDOI

How does the cosmic web impact assembly bias

TL;DR: In this article, the mass, accretion rate, and formation time of dark matter halos near protofilaments are analytically predicted using a conditional version of the excursion set approach in its so-called upcrossing approximation.
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Cosmic web anisotropy is the primary indicator of halo assembly bias

TL;DR: In this paper, it was shown that the internal properties of dark matter haloes correlate with the large-scale halo clustering strength at fixed halo mass, and are also strongly affected by the local, non-linear cosmic web.
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The three causes of low-mass assembly bias

TL;DR: In this paper, the authors present a detailed analysis of the physical processes that cause halo assembly bias and show that splashback subhaloes are responsible for two thirds of the assembly bias signal, but do not account for the entire effect.
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Efficient computation of galaxy bias with neutrinos and other relics

TL;DR: ReliefFast as discussed by the authors finds that the bias induced by light relics partially compensates the suppression of power, and should be accounted for in any search for relics with galaxy data, at little computational cost.
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The multidimensional dependence of halo bias in the eye of a machine: a tale of halo structure, assembly, and environment

TL;DR: In this article, the bias is a multivariate function of halo properties that falls into three regimes: early-forming, low-mass and late-forming haloes, and the bias depends sensitively on the recent mass accretion history.
References
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Journal ArticleDOI

A kinematic classification of the cosmic web

TL;DR: In this paper, a new approach for the classification of the cosmic web is presented, which is based on the analysis of the velocity shear tensor rather than the gravitational tidal tensor, and is applied to a dark matter only simulation of a box of side length 64 h−1 Mpc and N = 10243 particles within the 5-year Wilkinson and Microwave Anisotropy Probe/Λ cold dark matter (ΛCDM) model.
Journal ArticleDOI

The dependence of dark halo clustering on the formation epoch and the concentration parameter

TL;DR: In this paper, the age-dependence of dark matter halo clustering was examined using a set of 7 high-resolution cosmological simulations each with $N=1024^3$ particles.
Journal ArticleDOI

Tidal effects and the environment dependence of halo assembly

TL;DR: In this paper, the authors explore a possible origin for the puzzling anti-correlation between the formation epoch of galactic dark-matter haloes and their environment density and find that a primary driver of suppressed growth, by accretion and mergers, is tidal effects dominated by a neighbouring massive halo.
Journal ArticleDOI

Hunting down horizon-scale effects with multi-wavelength surveys

TL;DR: In this article, a multi-wavelength combination of large volume surveys is proposed to detect general relativistic (GR) effects on the galaxy power spectrum, which can be detected with a signal-to-noise of about $14.
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