Is there a disk of satellites around the Milky Way?
  The "Disk of satellites" (DoS) around Milky Way is a highly debated topic
with conflicting interpretations of observations and their theoretical models.
We perform a comprehensive analysis of all dwarfs detected in the Milky Way and
find that the DoS structure depends strongly on the plane identification method
and the sample size. In particular, we demonstrate that a smaller sample size
produces a higher anisotropy of the spatial distribution and a stronger
clustering of the angular momentum of the satellites. Moreover, we calculate
the evolution of the 11 classical satellites with proper motion measurements
and find that the thin DoS they currently reside in is transient. Furthermore,
we analyze two cosmological simulations using the same initial conditions of a
Milky Way-sized galaxy, an N-body run with dark matter only and a hydrodynamic
one with both baryonic and dark matter, and find that the hydrodynamic
simulation produces more anisotropic distribution of satellites than the N-body
one. Our results suggest that an anisotropic distribution of satellites in
galaxies can originate from baryonic processes in the hierarchical structure
formation model, but the claimed highly-flattened, coherently-rotating DoS of
the Milky Way may be a small-number selection effect. These findings may help
resolve the contradictory claims of DoS in other galaxies and the discrepancy
among numerical simulations.
