leading arm of the stream, a position that is much more heavily populated after the Clouds have completed one full orbit around the Galaxy.

Proper motions: conclusive proof of Magellanic origin {#SecPropMot}
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Ultimately, the most compelling evidence for LMC association will come from the proper motions of the new dwarfs. This is because all material associated with the LMC before infall is expected to retain the direction of its orbital angular momentum. In other words, to first order, Galactic tides are not expected to torque the LMC or its debris away from their original orbital plane.

We show this in Fig. \[fig:poles\], where we plot the [*direction*]{} of the orbital angular momentum of LMCa particles at first pericenter. The innermost and outermost isodensity contours enclose $5\%$, and $95\%$ of all LMCa particles, respectively, and are centered at the location of the LMC orbital pole (central grey square). The other grey square (at $b=-20^\circ$ and $l=175^\circ$) corresponds to the SMC, and is consistent with its assumed association with the LMC.

![Sky coordinates of the orbital poles (i.e., the direction of the orbital angular momentum) of particles associated with LMCa. Contours show constant density lines for the distribution of all LMCa. 