Dark Matter Halo Properties vs. Local Density and Cosmic Web Location

TL;DR

This study uses cosmological simulations to show that dark matter halo properties are primarily influenced by local density rather than their specific cosmic web environment, aligning with galaxy survey observations.

Contribution

It demonstrates that halo properties are unaffected by web environment types when controlling for local density, clarifying the role of environment in halo evolution.

Findings

Halo properties are independent of web environment at fixed density.

Environmental density is the main factor influencing halo characteristics.

Galaxy halos near cosmic walls show no significant property differences except orientation.

Abstract

We study the effects of the local environmental density and the cosmic web environment (filaments, walls, and voids) on key properties of dark matter halos using the Bolshoi-Planck LCDM cosmological simulation. The z = 0 simulation is analysed into filaments, walls, and voids using the SpineWeb method and also the VIDE package of tools, both of which use the watershed transform. The key halo properties that we study are the specific mass accretion rate, spin parameter, concentration, prolateness, scale factor of the last major merger, and scale factor when the halo had half of its z = 0 mass. For all these properties, we find that there is no discernible difference between the halo properties in filaments, walls, or voids when compared at the same environmental density. As a result, we conclude that environmental density is the core attribute that affects these properties. This conclusion is in line with recent findings that properties of galaxies in redshift surveys are independent of their cosmic web environment at the same environmental density at z ~ 0. We also find that the local web environment of the Milky Way and the Andromeda galaxies near the centre of a cosmic wall does not appear to have any effect on the properties of these galaxies' dark matter halos except for their orientation, although we find that it is rather rare to have such massive halos near the centre of a relatively small cosmic wall.