Magellanic Mayhem: Metallicities and Motions
  We assemble a catalogue of Magellanic Cloud red giants from Data Release 2 of
the $Gaia$ mission and, utilising machine learning methods, obtain photometric
metallicity estimates for them. In doing so, we are able to chemically map the
entirety of the Magellanic System at once. Our high resolution maps reveal a
plethora of substructure, with the Large Magellanic Cloud (LMC) bar and spiral
arm being readily apparent. We uncover a curious spiral-like feature in the
southern portion of the LMC disc, hosting relatively metal-rich giants and
likely a by-product of historic encounter with the Small Magellanic Cloud
(SMC). Modelling the LMC as an inclined thin disc, we find a shallow
metallicity gradient of $-0.048 \pm 0.001$ dex/kpc out to $\sim 12^{\circ}$
from the centre of the dwarf. We see evidence that the Small Magellanic Cloud
is disrupting, with its outer iso-density contours displaying the S-shape
symptomatic of tidal stripping. On studying the proper motions of the SMC
giants, we observe a population of them being violently dragged towards the
larger Cloud. The perturbed stars predominately lie in front of the SMC, and we
interpret that they exist as a tidal tail of the dwarf, trailing in its motion
and undergoing severe disruption from the LMC. We find the metallicity
structure in the Magellanic Bridge region to be complex, with evidence for a
composite nature in this stellar population, consisting of both LMC and SMC
debris.
