The Void in the Sculptor Group Spiral Galaxy NGC 247
  The dwarf galaxy NGC 247, located in the Sculptor Filament, displays an
apparent void on the north side of its spiral disk. The existence of the void
in the disk of this dwarf galaxy has been known for some time, but the exact
nature and cause of this strange feature has remained unclear. We investigate
the properties of the void in the disk of NGC 247 using photometry of archival
Hubble Space Telescope data to analyze the stars in and around this region.
Based on a grid of isochrones from log(t)=6.8 to log(t)=10.0, we assign ages
using nearest-neighbor interpolation. Examination of the spatial variation of
these ages across the galaxy reveals an age difference between stars located
inside the void region and stars located outside this region. We speculate that
the void in NGC 247's stellar disk may be due to a recent interaction with a
nearly dark sub-halo that collided with the disk and could account for the
long-lived nature of the void.
