The Mysterious Sickle Object in the Carina Nebula: A stellar wind
  induced bow shock grazing a clump?
  Optical and near-infrared images of the Carina Nebula show a peculiar
arc-shaped feature, which we call the "Sickle", next to the B-type star
Trumpler 14 MJ 218. We use multi-wavelength observations to explore and
constrain the nature and origin of the nebulosity. Using sub-mm data from
APEX/LABOCA as well as Herschel far-infrared maps, we discovered a dense,
compact clump with a mass of ~ 40 Msun located close to the apex of the Sickle.
We investigate how the B-star MJ 218, the Sickle, and the clump are related.
Our numerical simulations show that, in principle, a B-type star located near
the edge of a clump can produce a crescent-shaped wind shock front, similar to
the observed morphology. However, the observed proper motion of MJ 218 suggest
that the star moves with high velocity (~ 100 km/s) through the ambient
interstellar gas. We argue that the star is just about to graze along the
surface of the clump, and the Sickle is a bow shock induced by the stellar
wind, as the object moves supersonically through the density gradient in the
envelope of the clump.
