  We present 3D smoothed particle hydrodynamics simulations of the collapse of
clumps formed through gravitational instability in the outer part of a
protoplanetary disc. The initial conditions are taken directly from a global
disc simulation, and a realistic equation of state is used to follow the clumps
as they contract over several orders of magnitude in density, approaching the
molecular hydrogen dissociation stage. The effects of clump rotation,
asymmetries, and radiative cooling are studied. Rotation provides support
against fast collapse, but non-axisymmetric modes develop and efficiently
transport angular momentum outward, forming a circumplanetary disc. This
transport helps the clump reach the dynamical collapse phase, resulting from
molecular hydrogen dissociation, on a thousand-year timescale, which is smaller
than timescales predicted by some previous spherical 1D collapse models.
Extrapolation to the threshold of the runaway hydrogen dissociation indicates
that the collapse timescales can be shorter than inward migration timescales,
suggesting that clumps could survive tidal disruption and deliver a proto-gas
giant to distances of even a few AU from the central star.
