http://arxiv.org/abs/1510.00096
We have analyzed the Magellanic Stream (MS) using the deepest and the most resolved HI survey of the Southern Hemisphere (GASS). The overall Stream is structured into two filaments suggesting two ram-pressure tails lagging behind the Magellanic Clouds (MCs), and resembling two close, transonic, von Karman vortex streets. The past motions of the Clouds appear imprinted in them, implying almost parallel initial orbits, and then a radical change after their passage near the N(HI) peak of the MS. This is consistent with a recent collision between the MCs, 200-300 Myr ago, which has stripped further their gas into small clouds, spreading them out along a gigantic bow-shock, perpendicular to the MS. The Stream is formed by the interplay between stellar feedback and the ram-pressure exerted by Milky Way (MW) halo hot gas with $n_h$= $10^{-4}$ $cm^{-3}$ at 50-70 kpc, a value necessary for explaining the MS multiphase high-velocity clouds. The corresponding hydrodynamical modeling provides the currently most accurate reproduction of the whole HI Stream morphology, of its velocity, and column density profiles along $L_{MS}$. The ‘ram-pressure plus collision’ scenario requires tidal dwarf galaxies (TDGs), which are assumed to be the Cloud and dSph progenitors having let imprints into the MS and the Leading Arm, respectively. The simulated LMC and SMC have baryonic mass, kinematics and proper motions consistent with observations. This supports a novel paradigm for the Magellanic Stream System, which could take its origin from material expelled towards the MW by the ancient gas-rich merger that formed M31.
F. Hammer, Y. Yang, H. Flores, et. al.
Fri, 2 Oct 15
18/43
Comments: 20 pages, 16 Figures, 3 Tables; Astrophysical Journal, accepted; Figures 10 and 13 are available in video format at this http URL