The Magellanic Stream at 20 kpc: A New Orbital History for the Magellanic Clouds

Abstract

We present new simulations of the formation of the Magellanic Stream based on an updated first-passage interaction history for the Magellanic Clouds, including both the Galactic and Magellanic Coronae and a live dark matter halo for the Milky Way. This new interaction history is needed because previously successful orbits need updating to account for the Magellanic Corona and the loosely bound nature of the Magellanic Group. These orbits involve two tidal interactions over the last 3.5 Gyrs and reproduce the Stream's position and appearance on the sky, mass distribution, and velocity profile. Most importantly, our simulated Stream is only $\sim$20 kpc away from the Sun at its closest point, whereas previous first-infall models predicted a distance of $100-200$ kpc. This dramatic paradigm shift in the Stream's 3D position would have several important implications. First, estimates of the observed neutral and ionized masses would be reduced by a factor of $\sim$5. Second, the stellar component of the Stream is also predicted to be $<$20 kpc away. Third, the enhanced interactions with the MW's hot corona at this small distance would substantially shorten the Stream's lifetime. Finally, the MW's UV radiation field would be much stronger, potentially explaining the H$\alpha$ emission observed along most of the Stream. Our prediction of a 20 kpc Stream could be tested by searching for UV absorption lines towards distant MW halo stars projected onto the Stream.

11 pages, 4 figures. Published in ApJL at https://iopscience.iop.org/article/10.3847/2041-8213/ac3338. Movies and interactive figures available at https://github.com/DOnghiaGroup/lucchini-2021-movies

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• Radiative Turbulent Mixing Layers and the Survival of Magellanic Debris
• Structural and Dynamical Analysis of the Quiescent Molecular Ridge in the Large Magellanic Cloud
• The signature of large scale turbulence driving on the structure of the interstellar medium
• A Tilt in the Dark Matter Halo of the Galaxy