Day 1094

Friday.

1605.03574
Identifying true satellites of the Magellanic Clouds
Sales, Navarro, Kallivayalil, Frenk

The hierarchical nature of LCDM suggests that the Magellanic Clouds must have been surrounded by a number of satellites before their infall into the MW.  Many of those satellite should still be in close proximity to the Clouds, but some could have dispersed ahead/behind the Clouds along their Galactic orbit.  Either way, prior association with the Clouds results in strong restrictions on the present-day positions and velocities of candidate Magellanic satellites: they must lie close to the nearly-polar orbital plane of the Magellanic stream, and their distances and radial velocities must follow the latitude dependence expected for a tidal stream with the Clouds at pericenter.  Use a cosmo numerical sim of the disruption of massive sub halo in a MW-sized LCDM halo to test whether any of the 20 dwarfs recently-discovered in the DES, SMASH, Pan-STARRS, and ATLAS surveys are truly associated with the Clouds.  Of the 6 systems with kinematic data, only Hydra II and Hor 1 have distances and radial velocities consistent with a Magellanic origin.  Of the remaining dwarfs, six (Hor2, Eri3, Ret3, Tuc4, Tuc6, and Phx2) have positions and distances consistent with a Magellanic origin, but kinematic data are needed to substantiate that possibility.  Conclusive evidence for association would require proper motions to constrain the orbital angular momentum direction, which, for true Magellanic satellites, must coincide with that of the Clouds.  Use this result to predict radial velocities and proper motions for all new dwarfs.  The results are relatively insensitive to the assumption of first or second pericenter for the Clouds.