Dark matter halo properties versus local density and cosmic web location

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 haloes using the Bolshoi-Planck cold dark matter cosmological simulation. The z = 0simulationisanalysedintofilaments, 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 = 0m a s s .F o ra l lt h e s ep r o p e r t i e s , 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 around galaxies of Milky Way's and Andromeda's masses that are near the centre of a cosmic wall does not appear to have any effect on the properties of those galaxies' dark matter haloes except on their orientation, although we find that it is rather rare to have such massive haloes near the centre of a relatively small cosmic wall.

Probing Galaxy assembly bias in BOSS galaxies using void probabilities

“…However, Figure 4 shows that the type of assembly bias imparted in this model is within our parameter space. Additionally, Goh et al (2019) find that the properties of dark matter halos, once controlling for large-scale density, are indepen- dent of the details of the halo's location within the cosmic web-i.e., filaments, walls, nodes, sheets, etc. Thus there is not more information beyond ρ required when implementing assembly bias.…”

Revealing the Dark Threads of the Cosmic Web

“…Therefore, we truncated the simulation data to a width of approximately 70 Mpc in one direction centered on the median luminosity distance of our galaxy sample, which would ease the computational load when fitting the BP data with the MCPM algorithm. Specifically, we used two BP data products in our analysis: a halo catalog produced using the Rockstar algorithm (Behroozi et al 2013) and a datacube containing the dark matter density field smoothed over 0.25 Mpc scales (Goh et al 2019;Lee et al 2017).…”

The Sheet of Giants: Unusual properties of the Milky Way’s immediate neighbourhood

“…In addition, they required that each wall contains at least one halo in the the mass range 0.7 − 1.3 × 10 12 M and a number of other criteria such as the existence of a pair of haloes, the separation between them, etc. We believe that the conclusion of Goh et al (2019) about the extreme rarity of the Local Sheet was largely due to the restrictive set of many criteria and the method used to estimate the incidence of LV-like environments in ΛCDM in such a high number of dimensions. This is an important point because similar approaches for estimating the incidence of systems with specific properties arise in other contexts, such as estimating the rarity of 'satellite planes' (see, e.g.…”

“…We illustrate this at the end of Section 5. To be fair, Goh et al (2019) do consider the incidence of Local Volume properties using smaller numbers of restrictions. In particular, they consider the rarity of 'wall'-type environments without additional restrictive constraints and point out that only ≈ 25 per cent of Milky Way-sized haloes reside in wall regions, which is similar to our estimate that 20 per cent of LV analogues lie outside the isodensity contour that intersects the Local Volume in c/a − b/a space (see Table 4).…”

“…In this regard, it is notable that Goh et al (2019) studied the incidence of ≈ 4h −1 Mpc 'walls' in the Bolshoi-Planck ΛCDM simulation and argued that such walls are exceedingly rare, which would make modelling them challenging. If LV-like environments are truly rare and also significantly influence the properties of the galaxies within them, this could be behind the rarity of the flattened satellite configurations found in ΛCDM simulations.…”