Dynamically Produced Moving Groups in Interacting Simulations

TL;DR

This study demonstrates that dwarf galaxy interactions with a Milky Way-like disk can generate large moving groups in the stellar disk, with simulations revealing more groups than in isolated cases, suggesting a link to observed Milky Way structures.

Contribution

The paper introduces a new algorithm for identifying large moving groups in stellar velocity space and shows that dwarf galaxy interactions significantly increase their formation.

Findings

Interacting simulations produce more moving groups than isolated ones.

Dwarf galaxies induce large moving groups similar to those observed in the Milky Way.

Some Milky Way moving groups may originate from dwarf galaxy interactions.

Abstract

We show that Smoothed Particle Hydrodynamics (SPH) simulations of dwarf galaxies interacting with a Milky Way-like disk produce moving groups in the simulated stellar disk. We analyze three different simulations: one that includes dwarf galaxies that mimic the Large Magellanic Cloud, Small Magellanic Cloud and the Sagittarius dwarf spheroidal; another with a dwarf galaxy that orbits nearly in the plane of the Milky Way disk; and a null case that does not include a dwarf galaxy interaction. We present a new algorithm to find large moving groups in the $V_R, V_\phi$ plane in an automated fashion that allows us to compare velocity sub-structure in different simulations, at different locations, and at different times. We find that there are significantly more moving groups formed in the interacting simulations than in the isolated simulation. A number of dwarf galaxies are known to orbit the Milky Way, with at least one known to have had a close pericenter approach. Our analysis of simulations here indicates that dwarf galaxies like those orbiting our Galaxy produce large moving groups in the disk. Our analysis also suggests that some of the moving groups in the Milky Way may have formed due to dynamical interactions with perturbing dwarf satellites. The groups identified in the simulations by our algorithm have similar properties to those found in the Milky Way, including similar fractions of the total stellar population included in the groups, as well as similar average velocities and velocity dispersions.