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Abstract: We present results from neutral hydrogen HI observations of the tip of theMagellanic Stream MS, obtained with the Arecibo telescope as a part of theon-going survey by the Consortium for Galactic studies with the Arecibo L-bandFeed Array. We find four large-scale, coherent HI streams, extendingcontinously over a length of 20 degrees, each stream possessing differentmorphology and velocity gradients. The newly discovered streams provide strongsupport for the tidal model of the MS formation by Connors et al. 2006, whichsuggested a spatial and kinematic bifurcation of the MS. The observedmorphology and kinematics suggest that three of these streams could beinterpreted as a 3-way splitting of the main MS filament, while the fourthstream appears much younger and may have originated from the Magellanic Bridge.We find an extensive population of HI clouds at the tip of the MS. Two thirdsof clouds have an angular size in the range 3.5-10-. We interpret this asbeing due to thermal instability, which would affect a warm tail of gastrailing through the Galactic halo over a characteristic timescale of a fewMyrs to a few hundred Myrs. We show that thermal fragments can survive in thehot halo for a long time, especially if surrounded by a <10^6 K halo gas. Ifthe observed clumpy structure is mainly due to thermal instability, then thetip of the MS is at a distance of ~70 kpc. A significant fraction of HI cloudsat the tip of the MS show multi-phase velocity profiles, indicating theco-existence of cooler and warmer gas.

Author: Snezana Stanimirovic, Samantha Hoffman UW Madison, Carl Heiles UC Berkeley, Kevin A. Douglas SSL, UC Berkeley, Mary Putman Univ.


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