A Study of the Properties and Dynamics of the Disk of Satellites in a Milky-Way-like Galaxy System

TL;DR

This study uses high-resolution simulations with baryon physics to analyze the properties and dynamics of satellite disks in Milky-Way-like galaxies, revealing anisotropic distributions and infall-dominated structures.

Contribution

It provides the first detailed analysis of satellite disk properties in high-resolution baryonic simulations based on Aquarius initial conditions.

Findings

Satellites are anisotropically distributed around the galaxy.

The satellite disk is not rotationally supported and is composed of infalling sub-halos.

The angular momentum of the satellite system differs from the disk normal.

Abstract

The dynamics of the satellite systems of Milky-Way-like galaxies offer a useful means by which to study the galaxy formation process in the cosmological context. It has been suggested that the currently observed anisotropic distribution of the satellites in such galaxy systems is inconsistent with the concordance $\Lambda CDM$ cosmology model on the galactic scale if the observed satellites are random samples of the dark matter (DM) sub-halos that are nearly isotropically distributed around the central galaxy. In this study, we present original high-resolution zoom-in studies of central galaxies and satellite systems based upon initial conditions for the DM distribution from the Aquarius simulations but with substantial high-resolution baryon physics added. We find that the galaxy most like the Milky Way in this study does indeed contain a disk of satellites (DOS). Although one galaxy DOS system does not answer the question of how common such disks are, it does allow the opportunity to explore the properties and dynamics of the DOS system. Our investigation centers on the spatial arrangement (distances, angles, etc.) of satellites in this Milky-Way-like galaxy system with a specific emphasis on identifying and analyzing the disk-like structure along with its dynamical and morphological properties. Among the conclusions from this study, we find that the satellites and DM sub-halos in the galaxy simulations are anisotropically distributed. The dynamical properties of the satellites, however, indicate that the direction of the angular momentum vector of the whole satellite system is different from the normal direction of the fitted DOS and from the normal direction of the velocity dispersion of the system. Hence, the fitted DOS appears to be comprised of infalling sub-halos and is not a rotationally supported system.