An Interaction of a Magellanic Leading Arm High-Velocity Cloud with the Milky Way Disk

The Leading Arm of the Magellanic system is a tidally formed H I feature extending ~60° from the Magellanic Clouds ahead of their direction of motion. Using atomic hydrogen (H I) data from the Galactic All-Sky Survey (GASS), supplemented with data from the Australia Telescope Compact Array, we have found evidence for an interaction between a cloud in the Leading Arm and the Galactic disk where the Leading Arm crosses the Galactic plane. The interaction occurs at velocities permitted by Galactic rotation, which allows us to derive a kinematic distance to the cloud of 21 kpc, suggesting that the Leading Arm crosses the Galactic plane at a Galactic radius of R ≈ 17 kpc.