On the Origin of Dynamically Cold Rings Around the Milky Way

TL;DR

This paper proposes that high-eccentricity satellite flybys can produce long-lasting, cold, ring-like structures around the Milky Way, similar to the Monoceros ring, offering a cosmologically motivated formation scenario.

Contribution

It introduces a new formation mechanism for galactic rings via high-eccentricity flybys, supported by simulations matching observed properties of the Monoceros ring.

Findings

Flybys produce persistent, cold ring-like features on low-eccentricity orbits.

Simulated rings match the distribution and kinematics of the Monoceros ring.

High-eccentricity flybys are a plausible cosmological origin for such rings.

Abstract

We present a scenario for the production of dynamically cold rings around the Milky Way via a high-eccentricity, flyby encounter. These initial conditions are more cosmologically motivated than those considered in previous works. We find that the encounters we examine generically produce a series of nearly dynamically cold ring-like features on low-eccentricity orbits that persist over timescales of ~2-4 Gyr via the tidal response of the primary galaxy to the close passage of the satellite. Moreover, they are both qualitatively and quantitatively similar to the distribution, kinematics, and stellar population of the Monoceros ring. Therefore, we find that a high eccentricity flyby by a satellite galaxy represents a cosmologically appealing scenario for forming kinematically distinct ring-like features around the Milky Way.