Mapping the Tidal Disruption of the Hercules Dwarf: A Wide-Field DECam
  Imaging Search for RR Lyrae Stars
  We investigate the hypothesized tidal disruption of the Hercules ultra-faint
dwarf galaxy (UFD). Previous tidal disruption studies of the Hercules UFD have
been hindered by the high degree of foreground contamination in the direction
of the dwarf. We bypass this issue by using RR Lyrae stars, which are standard
candles with a very low field-volume density at the distance of Hercules. We
use wide-field imaging from the Dark Energy Camera on CTIO to identify
candidate RR Lyrae stars, supplemented with observations taken in coordination
with the Beijing-Arizona Sky Survey on the Bok Telescope. Combining color,
magnitude, and light-curve information, we identify three new RR Lyrae stars
associated with Hercules. All three of these new RR Lyrae stars lie outside its
published tidal radius. When considered with the nine RR Lyrae stars already
known within the tidal radius, these results suggest that a substantial
fraction of Hercules' stellar content has been stripped. With this degree of
tidal disruption, Hercules is an interesting case between a visibly disrupted
dwarf (such as the Sagittarius dwarf spheroidal galaxy) and one in dynamic
equilibrium. The degree of disruption also shows that we must be more careful
with the ways we determine object membership when estimating dwarf masses in
the future. One of the three discovered RR Lyrae stars sits along the minor
axis of Hercules, but over two tidal radii away. This type of debris is
consistent with recent models that suggest Hercules' orbit is aligned with its
minor axis.
