Signatures of broken protoplanetary discs in scattered light and in
  sub-millimetre observations
  Spatially resolved observations of protoplanetary discs are revealing that
their inner regions can be warped or broken from the outer disc. A few
mechanisms are known to lead to such 3D structures; among them, the interaction
with a stellar companion. We perform a 3D SPH simulation of a circumbinary disc
misaligned by $60^\circ$ with respect to the binary orbital plane. The inner
disc breaks from the outer regions, precessing as a rigid body, and leading to
a complex evolution. As the inner disc precesses, the misalignment angle
between the inner and outer discs varies by more than $100^\circ$. Different
snapshots of the evolution are post-processed with a radiative transfer code,
in order to produce observational diagnostics of the process. Even though the
simulation was produced for the specific case of a circumbinary disc, most of
the observational predictions hold for any disc hosting a precessing inner rim.
Synthetic scattered light observations show strong azimuthal asymmetries, where
the pattern depends strongly on the misalignment angle between inner and outer
disc. The asymmetric illumination of the outer disc leads to azimuthal
variations of the temperature structure, in particular in the upper layers,
where the cooling time is short. These variations are reflected in asymmetric
surface brightness maps of optically thick lines, as CO $J$=3-2. The
kinematical information obtained from the gas lines is unique in determining
the disc structure. The combination of scattered light images and (sub-)mm
lines can distinguish between radial inflow and misaligned inner disc
scenarios.
