Eight Ultra-faint Galaxy Candidates Discovered in Year Two of the Dark
  Energy Survey
  We report the discovery of eight new ultra-faint dwarf galaxy candidates in
the second year of optical imaging data from the Dark Energy Survey (DES). Six
of these candidates are detected at high confidence, while two lower-confidence
candidates are identified in regions of non-uniform survey coverage. The new
stellar systems are found by three independent automated search techniques and
are identified as overdensities of stars, consistent with the isochrone and
luminosity function of an old and metal-poor simple stellar population. The new
systems are faint (Mv > -4.7 mag) and span a range of physical sizes (17 pc <
$r_{1/2}$ < 181 pc) and heliocentric distances (25 kpc < D < 214 kpc). All of
the new systems have central surface brightnesses consistent with known
ultra-faint dwarf galaxies (\mu < 27.5 mag arcsec$^{-2}$). Roughly half of the
DES candidates are more distant, less luminous, and/or have lower surface
brightnesses than previously known Milky Way satellite galaxies. Most of the
candidates are found in the southern part of the DES footprint close to the
Magellanic Clouds. We find that the DES data alone exclude (p < 0.001) a
spatially isotropic distribution of Milky Way satellites and that the observed
distribution can be well, though not uniquely, described by an association
between several of the DES satellites and the Magellanic system. Our model
predicts that the full sky may hold ~100 ultra-faint galaxies with physical
properties comparable to the DES satellites and that 20-30% of these would be
spatially associated with the Magellanic Clouds.
