An anti-correlation between barycentre offsets and velocity dispersion for highest overdensity subhalos in cosmological simulations

TL;DR

This study reveals an anti-correlation between barycentre offsets and velocity dispersion in high-overdensity subhalos within cosmological simulations, with implications for understanding halo dynamics and structure.

Contribution

It presents the first detailed analysis of the relationship between barycentre offsets and velocity dispersion in high-overdensity subhalos using hydrodynamic simulations.

Findings

Larger barycentre offsets are more common in less massive, higher redshift halos.

Subhalos with higher velocity dispersion tend to have smaller barycentre offsets.

The anti-correlation is more significant at redshift z=0.

Abstract

In this paper, we use two hydrodynamic simulations to study the barycentre offsets $r_{{\rm off}}$ between the entire halo and the gas or dark matter subhalo with largest overdensity. We restrict our analysis to those halos with large rescaled offsets, i.e. $r_{{\rm off}}/r_{200}\gtrsim 0.05$. The halos which are less massive and at higher redshifts are more likely to have larger $r_{{\rm off}}/r_{200}$. The 3D velocity dispersion of the subhalos with largest overdensity is found to have a similar mass and redshift dependence as $r_{{\rm off}}/r_{200}$. We also find that the gas subhalos with maximum overdensity and larger gas velocity dispersion $\sigma_{v}^{\rm ICM,sub}/\sigma_{200}$ tend to have smaller barycentre offsets $r_{{\rm off}}/r_{200}$. Similar result is found for the highest overdensity dark matter subhalos but with less significance. This anti-correlation is more significant for the snapshot $z=0$ than $z=0.2$ and $0.5$. The underlying physical mechanism for this anti-correlation remains to be explored.