We have studied the shadows of a Schwarzschild black hole surrounded by a
Bach-Weyl ring through the backward ray-tracing method. The presence of
Bach-Weyl ring leads to that the photon dynamical system is non-integrable and
then chaos would appear in the photon motion, which affects sharply the black
hole shadow. The size and shape the black hole shadow depend on the black hole
parameter, the Bach-Weyl ring mass and the Weyl radius between black hole and
ring. Some self-similar fractal structures also appear in the black hole
shadow, which originates from the chaotic lensing. We also study the change of
the image of Bach-Weyl ring with the ring mass and the Weyl radius. Finally, we
analyze the invariant manifolds of Lyapunov orbits near the fixed points and
discuss further the formation of the shadow of a Schwarzschild black hole with
Bach-Weyl ring.Comment: 16 pages,8 figures, the version published in EPJ
