Properties of dark matter haloes as a function of local environment density

Abstract

We study how properties of discrete dark matter halos depend on halo environment, characterized by the mass density around the halos on scales from 0.5 to 16 h −1 Mpc. We find that low mass halos (those less massive than the characteristic mass M C of halos collapsing at a given epoch) in high-density environments have lower accretion rates, lower spins, higher concentrations, and rounder shapes than halos in median density environments. Halos in median and low-density environments have similar accretion rates and concentrations, but halos in low density environments have lower spins and are more elongated. Halos of a given mass in high-density regions accrete material earlier than halos of the same mass in lower-density regions. All but the most massive halos in high-density regions are losing mass (i.e., being stripped) at low redshifts, which causes artificially lowered NFW scale radii and increased concentrations. Tidal effects are also responsible for the decreasing spins of low mass halos in high density regions at low redshifts z < 1, by preferentially removing higher angular momentum material from halos. Halos in low-density regions have lower than average spins because they lack nearby halos whose tidal fields can spin them up. We also show that the simulation density distribution is well fit by an Extreme Value Distribution, and that the density distribution becomes broader with cosmic time.

Major mergers between dark matter haloes – I. Predictions for size, shape, and spin

“…In future work, we will consider how these results extend to more complicated merger situations such as multiple mergers, or smooth but anisotropic accretion, with the goal of under-standing fully the dependence of halo shape on mass and environment that has been measured in cosmological simulations (e.g. Jing & Suto 2002;Allgood et al 2006;Maulbetsch et al 2007;Despali et al 2014;Lee et al 2017;Vega-Ferrero et al 2017).…”

UniverseMachine: The correlation between galaxy growth and dark matter halo assembly from z = 0−10

“…For central galaxies (i.e., the main galaxies in central haloes), several studies , Berti et al 2017, Wang et al 2018, and this study) have also found correlations between these galaxies' quenched fractions (i.e., the fraction not forming stars) and the surrounding environment. At the same time, environmental density strongly correlates with halo accretion rates (Hahn et al 2009;Behroozi et al 2014a;Lee et al 2017). This would again suggest a correlation (and again not necessarily causation) between central galaxies' star formation rates and their host halo matter accretion rates.…”

Bubble mapping with the Square Kilometre Array – I. Detecting galaxies with Euclid, JWST, WFIRST, and ELT within ionized bubbles in the intergalactic medium at z &gt; 6

“…In simulations, both the shape of the dark halo mass function and the properties of individual halos of a given mass (in terms of accretion rate, spin, concentration and shapes) are predicted to be affected by the overdensity of the environment (Lee et al 2017), and increased merger rates, galaxy interactions and the feedback from ionizing radiation produced within overdense regions may further augment changes in galaxy properties compared to the field population.…”