Velocity fields and turbulence from cosmic filaments to galaxy clusters

TL;DR

This study uses high-resolution simulations of the Virgo galaxy cluster to analyze the velocity fields and turbulence within cosmic filaments, revealing a transition from compressive to solenoidal flows and energy spectrum variations.

Contribution

It provides the first detailed high-resolution analysis of velocity structures and turbulence in cosmic filaments connected to a galaxy cluster.

Findings

Velocity field transitions from compressive to solenoidal near the cluster core.

Energy spectrum steepens and increases in amplitude towards the cluster.

Filament turbulence characteristics vary with distance from the cluster.

Abstract

Galaxy clusters are currently the endpoint of the hierarchical structure formation; they form via the accretion of dark matter and cosmic gas from their local environment. In particular, filaments contribute grandly by accreting gas from cosmic matter sheets and underdense regions and feeding it to the galaxy clusters. Along the way, the gas in filaments is shocked and heated, which, together with the velocity structure within the filament, induces swirling and, thus, turbulence. In this work, we study a constrained hydrodynamical simulation replica of the Virgo cluster to characterise the velocity field in the two cosmic filaments connected to the cluster with unprecedented high resolution. First, we conduct a qualitative examination of slices extracted from the simulation. We study the temperature, the velocity field, and derived quantities in longitudinal cuts to study the general structure of the filaments and in transverse cuts to study their inner organisation and connection to cosmic matter sheets and underdense regions. Then, we conduct a quantitative study of velocities in Virgo's filaments by computing the 2D energy spectrum from 1 and 5~Mpc square maps extracted from the slices and centred on the core of the filaments. We show that the velocity field goes from mostly compressive far in the filaments to mostly solenoidal in Virgo's core. Moreover, we observe that the total energy spectrum in the filaments gains in amplitude and steepens towards Virgo.