The Lop-sided Spiral Galaxy NGC 247: Clues to a Possible Interaction
  with NGC 253
  Observations that span a broad range of wavelengths are used to examine
asymmetries in the disk of the nearby late-type spiral galaxy NGC 247. The
northern spiral arm is over-luminous at all wavelengths when compared with
other parts of the galaxy at similar galactocentric radii, while the density of
very luminous red stars in the void that is immediately south of this arm
matches that in other parts of the disk at the same galactocentric radius. Two
bubbles with spatial extents of many kpc are identified in the disk, and many
of the young stars in the southern disk of NGC 247 are located in the walls of
one of these structures. Dynamical age estimates of these bubbles coincide with
the last large-scale star formation event in the nucleus, suggesting that there
was large-scale star formation throughout the disk of NGC 247 a few hundred Myr
in the past. Morphological similarities are seen with the classical lop-sided
galaxy NGC 4027, and it is concluded that NGC 247 is a significantly lop-sided
spiral galaxy. The void in the northern disk is then the area between the main
body of the disk and the northern arm viewed in projection. The implications of
a lop-sided morphology for NGC 247 in the context of interactions with its
nearby starburst galaxy companion NGC 253 are discussed.
