# Evolution of mass and velocity filed in comic web: comparison between baryonic and dark matter

## TL;DR

This study examines the evolution of mass and velocity fields in the cosmic web for baryonic and dark matter from redshift 5 to 0, revealing similar trends with moderate differences and highlighting the development of structures and velocities over cosmic time.

## Contribution

It provides a detailed comparison of baryonic and dark matter evolution in the cosmic web using hydrodynamical simulations, focusing on the development of structures and velocity fields.

## Key findings

- Sheets formed early and set large-scale patterns by z=3
- Filaments became dominant structures at z~2-3
- Vorticity and velocity fields show hierarchical turbulence behavior

## Abstract

We investigate the evolution of cosmic web since $z=5$ in grid based cosmological hydrodynamical simulations, focusing on the mass and velocity field of both baryonic and cold dark matter. The tidal tensor of density is used as the main method for web identification, with $\lambda_{th}=0.2-1.2$. The evolution trends in baryonic and dark matter are similar, while moderate differences are observed. Sheets appeared early and their large scale pattern may have been set up by $z=3$. In term of mass, filaments superseded sheets as the primary collapsing structures at $z\sim2-3$. Tenuous filaments assembled with each other to form prominent ones at $z<~2$. In accordance with the construction of the frame of sheets, the cosmic divergence velocity, $v_{div}$, had been well developed above 2-3 Mpc by z=3. Afterwards, curl velocity, $v_{curl}$, grown dramatically along with the rising of filaments, become comparable to $v_{div}$, for $<2-3 Mpc$ at $z=0$. The scaling of $v_{curl}$ can be described by the hierarchical turbulence model. The alignment between vorticity and eigenvectors of shear tensor in baryonic matter field resembles dark matter, and is even moderately stronger between $\vec{\omega}$ and $\vec{e}_1$, and $\vec{e}_3$. Compared with dark matter, mildly less baryonic matter is found residing in filaments and clusters, and its vorticity has been developed more significantly below $2-3 Mpc$. These differences may be underestimated due to the limited resolution and lack of star formation in our simulation. The impact of the change of dominant structures in over-dense regions at $z\sim2-3$ on galaxy formation and evolution is shortly discussed.