# The Cosmic V-Web

## TL;DR

This paper explores the cosmic web by analyzing the velocity shear eigenvalues derived from radial peculiar velocities, providing a new visualization of cosmic structures like knots and filaments.

## Contribution

It introduces a method to visualize the cosmic velocity web using eigenvalues of the velocity shear from the Cosmicflows-2 data, employing Wiener filtering in the linear approximation.

## Key findings

- Identification of knots and filaments in the local cosmic web
- Visualization of the velocity web using iso-contours
- Application of Wiener filter to construct 3D velocity field

## Abstract

The network of filaments with embedded clusters surrounding voids seen in maps derived from redshift surveys and reproduced in simulations has been referred to as the cosmic web. A complementary description is provided by considering the shear in the velocity field of galaxies. The eigenvalues of the shear provide information on whether a region is collapsing in three dimensions, the condition for a knot, expanding in three-dimensions, the condition for a void, or in the intermediate condition of a filament or sheet. The structures that are quantitatively defined by the eigenvalues can be approximated by iso-contours that provide a visual representation of the cosmic velocity (V) web. The current application is based on radial peculiar velocities from the Cosmicflows-2 collection of distances. The three-dimensional velocity field is constructed using the Wiener filter methodology in the linear approximation. Eigenvalues of the velocity shear are calculated at each point on a grid. Here, knots and filaments are visualized across a local domain of diameter ~0.1c.