The Magellanic Edges Survey -- II. Formation of the LMC's northern arm
  The highly-substructured outskirts of the Magellanic Clouds provide ideal
locations for studying the complex interaction history between both Clouds and
the Milky Way (MW). In this paper, we investigate the origin of a >20$^\circ$
long arm-like feature in the northern outskirts of the Large Magellanic Cloud
(LMC) using data from the Magellanic Edges Survey (MagES) and Gaia EDR3. We
find that the arm has a similar geometry and metallicity to the nearby outer
LMC disk, indicating that it is comprised of perturbed disk material. Whilst
the azimuthal velocity and velocity dispersions along the arm are consistent
with those in the outer LMC, the in-plane radial velocity and out-of-plane
vertical velocity are significantly perturbed from equilibrium disk kinematics.
We compare these observations to a new suite of dynamical models of the
Magellanic/MW system, which describe the LMC as a collection of tracer
particles within a rigid potential, and the SMC as a rigid Hernquist potential.
Our models indicate the tidal force of the MW during the LMC's infall is likely
responsible for the observed increasing out-of-plane velocity along the arm.
Our models also suggest close LMC/SMC interactions within the past Gyr,
particularly the SMC's pericentric passage ~150 Myr ago and a possible SMC
crossing of the LMC disk plane ~400 Myr ago, likely do not perturb stars that
today comprise the arm. Historical interactions with the SMC prior to ~1 Gyr
ago may be required to explain some of the observed kinematic properties of the
arm, in particular its strongly negative in-plane radial velocity.
