  We present the results of high resolution SPH simulations of the evolution of
gravitationally unstable protoplanetary disks. We report on calculations in
which the disk is evolved using a locally isothermal or adiabatic equation of
state (with shock heating), and also on new simulations in which cooling and
heating by radiation are explicitly modeled. We find that disks with a minimum
Toomre parameter $< 1.4$ fragment into several gravitationally bound
protoplanets with masses from below to a few Jupiter masses. This is confirmed
also in runs where the disk is given a quiet start, growing gradually in mass
over several orbital times. A cooling time comparable to the orbital time is
needed to achieve fragmentation, for disk masses in the range $0.08-0.1
M_{\odot}$. After about 30 orbital times, merging between the bound
condensations always leads to 2-3 protoplanets on quite eccentric orbits.
