http://arxiv.org/abs/1911.11911
We revisit the orbital history of the Triangulum galaxy (M33) around the Andromeda galaxy (M31) in view of the recent Gaia Data Release 2 proper motion measurements for both Local Group galaxies. Earlier studies consider highly idealized dynamical friction, but neglect the effects of dynamical mass loss. We show the latter process to be important using orbit integrations and N-body simulations, which are mutually consistent. Contrary to previous claims that only a
first infall' is supported by the data, we find an orbital solution that brings these galaxies to within ~50 kpc of each other in the past, i.e. ~6.5 Gyr ago. We explore the implications of this finding using a N-body/hydrodynamical simulation to model the infall of M33 into M31 with a focus on the origin of two prominent features of this system: 1) M31's metal-rich Giant Stellar Stream; and 2) the M31-M33 HI filament. We find that the tidal interaction does not produce a stellar structure reminiscent of the stellar stream that survives up to the present day. The observed, outer disc warp in M33 may well be a relic of this past interaction. Similarly, the HI filament is likely a fossil structure dating back to the time of the ancient encounter between these galaxies. Our model implies the existence of a much larger, diffuse gas stream, theTriangulum stream’, that extends from M33 away from M31. We anticipate upcoming observations with the recently commissioned, Five-hundred-meter Aperture Spherical radio Telescope (FAST) that will target the putative stream in its first years of operation.
T. Tepper-García, J. Bland-Hawthorn and D. Li
Thu, 28 Nov 19
31/70
Comments: 12 pages
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