  The structures of confining vortices which underlie pure SU(3) Yang-Mills
theory are studied by means of lattice gauge theory. Vortices and Z_3 monopoles
are defined as dynamical degrees of freedom of the Z_3 gauge theory which
emerges by center gauge fixing and by subsequent center projection. It is
observed for the first time for the case of SU(3) that these degrees of freedom
are sensible in the continuum limit: the planar vortex density and the monopole
density properly scales with the lattice spacing. By contrast to earlier
findings concerning the gauge group SU(2), the effective vortex theory only
reproduces 62% of the full string tension. On the other hand, however, the
removal of the vortices from the lattice configurations yields ensembles with
vanishing string tension. SU(3) vortex matter which originates from Laplacian
center gauge fixing is also discussed. Although these vortices recover the full
string tension, they lack a direct interpretation as physical degrees of
freedom in the continuum limit.
