http://arxiv.org/abs/1906.04203
We employ the observed Gaia proper motions of the newly discovered Antlia 2 dwarf galaxy to calculate its orbital distribution in the cosmologically recent past. Using these observationally motivated orbits, we calculate the effect of the Antlia 2 dwarf galaxy on the outer HI disk of the Milky Way, using both test particle and Smoothed Particle Hydrodynamics simulations. We find that orbits with low pericenters, $\sim$ 10 kpc, produce disturbances that match the observed outer HI disk perturbations. We also show that the Sagittarius dwarf galaxy interaction does not match the observed perturbations in the outer gas disk. Thus, we argue that Antlia 2 is the likely driver of the observed large perturbations in the outer gas disk of the Galaxy. The current location of the Antlia 2 dwarf galaxy closely matches that predicted by an earlier dynamical analysis (Chakrabarti \& Blitz 2009) of the dwarf that drove ripples in the outer Galaxy, and, in particular, its orbit is nearly coplanar to the Galactic disk. If the Antlia 2 dwarf galaxy is responsible for the perturbations in the outer Galactic disk, it would have a specific range of proper motions that we predict here; this can be tested soon with Gaia DR-3 and Gaia DR-4 data.
S. Chakrabarti, P. Chang, A. Price-Whelan, et. al.
Wed, 12 Jun 19
58/59
Comments: submitted to ApJ Letters
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