Intergalactic filaments spin

TL;DR

This paper demonstrates that intergalactic filaments in the cosmic web exhibit significant rotation, challenging previous models and suggesting a potential role in magnetic field generation.

Contribution

It provides the first evidence from simulations that filaments themselves spin, adding a new dimension to understanding cosmic web dynamics.

Findings

Filaments rotate faster than random axes.

Rotation coherence extends along filaments.

Filament rotation may influence intergalactic magnetic fields.

Abstract

Matter in the Universe is arranged in a cosmic web, with a filament of matter typically connecting each neighbouring galaxy pair, separated by tens of millions of light-years. A quadrupolar pattern of the spin field around filaments is known to influence the spins of galaxies and haloes near them, but it remains unknown whether filaments themselves spin. Here, we measure dark-matter velocities around filaments in cosmological simulations, finding that matter generally rotates around them, much faster than around a randomly located axis. It also exhibits some coherence along the filament. The net rotational component is comparable to, and often dominant over, the known quadrupolar flow. The evidence of net rotations revises previous emphasis on a quadrupolar spin field around filaments. The full picture of rotation in the cosmic web is more complicated and multiscale than a network of spinning filamentary rods, but we argue that filament rotation is substantial enough to be an essential part of the picture. It is likely that the longest coherently rotating objects in the Universe are filaments. Also, we speculate that this rotation could provide a mechanism to generate or amplify intergalactic magnetic fields in filaments.