Counter-Orbiting Tidal Debris as the Origin of the MW DoS

TL;DR

This paper proposes that the Milky Way's satellite galaxies originate from tidal debris resulting from galaxy collisions, explaining their unusual distribution and orbital directions, including both co- and counter-orbiting satellites.

Contribution

It demonstrates that the phase-space distribution and orbital directions of MW satellites can be explained by tidal debris from galaxy mergers and fly-bys, a novel explanation for their origin.

Findings

Satellite distribution aligns with tidal debris predictions.

Both co- and counter-orbiting satellites can form from galaxy interactions.

Tidal debris can naturally produce the observed satellite orbital directions.

Abstract

The Milky Way satellite galaxies show a phase-space distribution that is not expected from the standard scenario of galaxy formation. This is a strong hint at them being of tidal origin, which would naturally explain their spacial distribution in a disc of satellites. It is shown that also their orbital directions can be reproduced with the debris of galaxy collisions. Both co- and counter-orbiting satellites are formed naturally in merger and fly-by interactions.