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Abstract: We explore the Magellanic Stream MS using a Gaussian decomposition of theHI velocity profiles in the Leiden-Argentine-Bonn LAB all-sky HI survey. Thisdecomposition exposes the MS to be composed of two filaments distinct bothspatially as first pointed out by Putman et al. and in velocity. Using thevelocity coherence of the filaments, one can be traced back to its origin inwhat we identify as the SouthEast HI Overdensity SEHO of the Large MagellanicCloud LMC, which includes 30 Doradus. Parts of the Leading Arm LA can alsobe traced back to the SEHO in velocity and position. Therefore, at leastone-half of the trailing Stream and most of the LA originates in the LMC,contrary to previous assertions that both the MS and the LA originate in theSmall Magellanic Cloud SMC and-or in the Magellanic Bridge. The two MSfilaments show strong periodic, undulating spatial and velocity patterns thatwe speculate are an imprint of the LMC rotation curve. If true, then the driftrate of the Stream gas away from the Magellanic Clouds is ~49 km-s and the ageof the MS is ~1.74 Gyr. The Staveley-Smith et al. high-resolution HI data ofthe LMC show gas outflows from supergiant shells in the SEHO that seem to becreating the LA and LMC filament of the MS. Blowout of LMC gas is an effect notpreviously accounted for but one that probably plays an important role increating the MS and LA.

Autor: David L. Nidever, Steven R. Majewski, W. Butler Burton


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