The cosmic web of the Local Universe: cosmic variance, matter content and its relation to galaxy morphology

TL;DR

This paper uses high-precision simulations to analyze the Local Universe's cosmic web environment, revealing typical cosmic variance, matter density profiles, and galaxy morphology distributions with high confidence, aligning with but refining previous findings.

Contribution

It introduces a novel constrained simulation-based characterization of the Local Universe, quantifies cosmic variance, and links galaxy morphology to cosmic web environments with improved confidence levels.

Findings

LU shows ~1σ scatter in cosmic web properties at >15 h^{-1} Mpc scales

Matter density profile of LU aligns with dark halo contributions, suggesting observational biases

Elliptical galaxies prefer clusters, while spirals favor voids, with high statistical significance

Abstract

We present, for the first time, a Local Universe (LU) characterization using high precision constrained $N$-body simulations based on self-consistent phase-space reconstructions of the large-scale structure in the Two-Micron All-Sky Galaxy Redshift Survey. We analyse whether we live in a special cosmic web environment by estimating cosmic variance from a set of unconstrained $\Lambda$CDM simulations as a function of distance to random observers. By computing volume and mass filling fractions for voids, sheets, filaments and knots, we find that the LU displays a typical scatter of about $1\sigma$ at scales $r>15\,h^{-1}\,{\rm Mpc}$, in agreement with $\Lambda$CDM, converging to a fair unbiased sample when considering spheres of about $60\,h^{-1}\,{\rm Mpc}$ radius. Additionally, we compute the matter density profile of the LU and found a reasonable agreement with the estimates of Karachentsev (2012) only when considering the contribution of dark haloes. This indicates that observational estimates may be biased towards low density values. As a first application of our reconstruction, we investigate the likelihood of different galaxy morphological types to inhabit certain cosmic web environments. In particular, we find that, irrespective of the method used to define the web, either based on the density or the peculiar velocity field, elliptical galaxies show a clear tendency to preferentially reside in clusters as opposed to voids (up to a level of $5.3\sigma$ and $9.8\sigma$ respectively) and conversely for spiral galaxies (up to a level of $5.6\sigma$ and $5.4\sigma$ respectively). These findings are compatible with previous works, albeit at higher confidence levels.