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Disk Destruction and (Re)-Creation in the Magellanic Clouds

Unlike most satellite galaxies in the Local Group that have long lost their gaseous disks, the Magellanic Clouds are gas-rich dwarf galaxies most-likely on their first pericentric passage allowing us to study disk evolution on the smallest scales. The Magellanic Clouds show both disk destruction and (re)-creation. The Large Magellanic Cloud has a very extended stellar disk reaching to at least 15 kpc (10 radial scalelengths) while its gaseous disk is truncated at ~5 kpc mainly due to its interaction with the hot gaseous halo of the Milky Way. The stellar disk of the Small Magellanic Cloud, on the other hand, has essentially been destroyed. The old stellar populations show no sign of rotation (being pressure supported) and have an irregular and elongated shape. The SMC has been severely disturbed by its close encounters with the LMC (the most recent only 200 Myr ago) which have also stripped out large quantities of gas creating much of the Magellanic Stream and the Magellanic Bridge. Amazingly, the SMC has an intact, rotating HI disk indicating that either the inner HI was preserved from destruction, or, more likely, that the HI disk reformed quickly after the last close encounter with the LMC.